4 months ago I got my PinePhonePro [1]. Since then I have got SE Linux working on it to the stage of allowing it to boot correctly with Debian/Unstable, login with the user_t domain (minimum privilege for the graphical user) and make and receive calls. I finished getting SE Linux working reasonably well 3 days ago and most (but not all) of the SE Linux policy is in Debian now. I’ve been getting good at Github PRs and I’m sending a lot of policy upstream, so the next version of Debian will have a much smaller diff from the upstream Refpolicy. I have been running the PinePhone with Plasma Mobile because I prefer KDE, I would run GNOME/Phoc if it gave significantly better functionality.

3 days ago I moved my main SIM (the one with the number that people call about work etc) to my PinePhone and tried running it as my main phone. Today I gave up on that.

My Android History

The last phone I had that did everything I needed was a Huawei Mate 10 Pro that I bought refurbished in June 2019 for $389. The Mate 10 Pro runs Android with the Google Play store and has been quite unremarkable which is presumably why I forgot to blog about it when I got it, it was a slight upgrade over the Huawei Mate 9 [2] that I had used for 2 years before that. In April 2022 I tried using a Huawei Nova 7i as my main phone without Google Play programs or services [3]. That experiment was a failure as I couldn’t get NextCloud to work for Calendaring and Contacts. It could be that I stuffed something up when trying that, but I put more skill and effort into trying to get it to work than most people ever would. The Nova 7i is a very slick phone, faster and nicer than the Mate 10 Pro (as expected being 2 years newer) while also having ridiculously long battery life. The Nova 7i when always on running the SchildiChat Matrix client and the Conversations Jabber client it will use less than 10% battery in a 8 hour work day.

As nice as the Nova 7i is for the core functions I still need to have Play Store apps for LinkedIn, Twitter, Facebook, Zoom, etc. Which meant connecting the Mate 10 Pro via Wifi. As slick as the Nova 7i is for non-Google stuff running it and the Mate 10 Pro is a medium amount of pain for a small amount of freedom.

So now I have for the moment abandoned the Nova 7i and gone back to the Mate 10 Pro. What I will try to do is to either forcibly install Google Play on the Nova 7i to make it my proprietary phone or to install an open distribution of Linux (IE not Android) to make it at least a small tablet which incidentally is much more powerful than a PinePhonePro.

Issues With the PinePhonePro

The battery charges very slowly (as much as 50 hours estimated charge time) and discharges fast. When used in a typical way in “Caffeine” mode to stop suspend so I can ssh to it etc it won’t come close to lasting an 8 hour day. Also it will only take 5V charging and ideally wants 5V 3A charging which most chargers won’t do. The charging speed over regular USB ports is very slow, sometimes stating it will take as much as 50 hours to charge. A phone that gets below 50% charge in less than 4 hours and can’t be charged at a reasonable speed from a USB port on a laptop or monitor is going to be a major pain to use in the office. I don’t think this can be fixed in software, we can alleviate it by making software more CPU efficient and by enabling various hardware sleep modes more effectively but the slow charging is a hardware issue that can’t be fixed.

The phone call quality is poor. Usually when on a call I hear static and sometimes the person at the other end appears to hear nothing. Also the UI for calls is different from Android which makes it take longer to answer a call and gives more missed calls. The UI issue is a combination of software and habits, both of which can be changed. But the call quality may be a hardware issue. I don’t know if it’s a hardware issue specific to my phone or something related to the PinePhonePro on the Telstra network.

Clicking on notification in the drop-down doesn’t take me to the app. I don’t know if this is regarded as a bug by the Plasma-Mobile developers. Also notifications aren’t displayed on the lock screen and there doesn’t seem to be a configuration option to enable this.

The Plasma-Mobile configuration for the wifi hotspot is difficult. There is no button for it in the drop-down menu (called Quicksettings in Plasma-Mobile) and no way of easily determining whether it’s in hotspot or wifi client mode. This isn’t an insurmountable problem and the worst-case is that I could write a script to do it, but it’s still annoying.

There is apparent support in the desktop version of KDE for syncing contacts from Google and I could probably get that working (although I failed last time I tried on the desktop), but it is a pain.

Conclusion

Most of the problems are software related and therefore I can get involved in solving them. I plan to keep working on these things. If all the software had worked in an ideal manner then I would have spent more time investigating the hardware issues of battery life and charge time and the quality of calls.

I now have my Librem5 [4] running Debian so I will be able to compare call quality with the PinePhonePro. If I’m unable to get the PinePhonePro working adequately then maybe making the Librem5 my main phone will be an option.

I hope that by early next year I will be able to make another test at using a FOSS phone my main phone. In the mean time I can still work on convergence and other things.

• [1] https://etbe.coker.com.au/2023/06/06/pinephonepro-first-impression/
• [2] https://etbe.coker.com.au/2017/12/14/huawei-mate9/
• [3] https://etbe.coker.com.au/2022/04/20/android-without-play/
• [4] https://etbe.coker.com.au/2022/03/19/more-librem5/

Laptop vs Desktop Price

Currently the smaller and cheaper USB-C docks start at about $25 and Dell has a new Vostro with 8G of RAM and 2*USB-C ports for $788. That gives a bit over $800 for a laptop and dock vs $795 for the cheapest Dell desktop which also has 8G of RAM. For every way of buying laptops and desktops (EG buying from Officeworks, buying on ebay, etc) the prices for laptops and desktops seem very similar. For all those comparisons the desktop will typically have a faster CPU and more options for PCIe cards, larger storage, etc. But if you don’t want to expand storage beyond the affordable 4TB NVMe/SSD devices, don’t need to add PCIe cards, and don’t need much CPU power then a laptop will do well. For the vast majority of the computer work I do my Thinkpad Carbon X1 Gen1 (from 2012) had plenty of CPU power.

If someone who’s not an expert in PC hardware was to buy a computer of a given age then laptops probably aren’t more expensive than desktops even disregarding the fact that a laptop works without the need to purchase a monitor, a keyboard, or a mouse. I can get regular desktop PCs for almost nothing and get parts to upgrade them very cheaply but most people can’t do that. I can also get a decent second-hand laptop and USB-C dock for well under $400.

Servers and Gaming Systems

For people doing serious programming or other compute or IO intensive tasks some variation on the server theme is the best option. That may be something more like the servers used by the r/homelab people than the corporate servers, or it might be something in the cloud, but a server is a server. If you are going to have a home server that’s a tower PC then it makes sense to put a monitor on it and use it as a workstation. If your server makes so much noise that you can’t spend much time in the same room or if it’s hosted elsewhere then using a laptop to access it makes sense.

Desktop computers for PC gaming makes sense as no-one seems to be making laptops with moderately powerful GPUs. The most powerful GPUs draw 150W which is more than most laptop PSUs can supply and even if a laptop PSU could supply that much there would be the issue of cooling. The Steam Deck [1] and the Nintendo Switch [2] can both work with USB-C docks. The PlayStation 5 [3] has a 350W PSU and doesn’t support video over USB-C. The Steam Deck can do 8K resolution at 60Hz or 4K at 120Hz but presumably the newer Steam games will need a desktop PC with a more powerful GPU to properly use such resolutions.

For people who want the best FPS rates on graphics intensive games it could make sense to have a tower PC. Also a laptop that’s run at high CPU/GPU use for a long time will tend to have it’s vents clogged by dust and possibly have the cooling fan wear out.

Monitor Resolution

Laptop support for a single 4K monitor became common in 2012 with the release of the Ivy Bridge mobile CPUs from Intel in 2012. My own experience of setting up 4K monitors for a Linux desktop in 2019 was that it was unreasonably painful and that the soon to be released Debian/Bookworm will make things work nicely for 4K monitors with KDE on X11. So laptop hardware has handled the case of a single high resolution monitor since before such monitors were cheap or common and before software supported it well. Of course at that time you had to use either a proprietary dock or a mini-DisplayPort to HDMI adaptor to get 4K working. But that was still easier than getting PCIe video cards supporting 4K resolution which is something that according to spec sheets wasn’t well supported by affordable cards in 2017.

Since USB-C became a standard feature in laptops in about 2017 support of more monitors than most people would want through a USB-C dock became standard. My Thinkpad X1 Carbon Gen5 which was released in 2017 will support 2*FullHD monitors plus a 4K monitor via a USB-C dock, I suspect it would do at least 2*4K monitors but haven’t had a chance to test. Cheap USB-C docks supporting this sort of thing have only become common in the last year or so.

How Many Computers per Home

Among middle class Australians it’s common to have multiple desktop PCs per household. One for each child who’s over the age of about 13 and one for the parents seems to be reasonably common. Students in the later years of high-school and university students are often compelled to have laptops so having the number of laptops plus the number of desktops be larger than the population of the house probably isn’t uncommon even among people who aren’t really into computers. As an aside it’s probably common among people who read my blog to have 2 desktops, a laptop, and a cloud server for their own personal use. But even among people who don’t do that sort of thing having computers outnumber people in a home is probably common.

A large portion of the computer users can do everything they need on a laptop. For gamers the graphics intensive games often run well on a console and that’s probably the most effective way of getting to playing the games. Of course the fact that there is “RGB RAM” (RAM with Red, Green, and Blue LEDs to light up) along with a lot of other wild products sold to gamers suggests that gaming PCs are not about what runs the game most effectively and that an art/craft project with the PC is more important than actually playing games.

Instead of having one desktop PC per bedroom and laptops for school/university as well it would make more sense to have a laptop per person and have a USB-C dock and monitor in each bedroom and a USB-C dock connected to a large screen TV in the lounge. This gives plenty of flexibility for moving around to do work and sharing what’s on your computer with other people. It also allows taking a work computer home and having work with your monitor, having a friend bring their laptop to your home to work on something together, etc.

For most people desktop computers don’t make sense. While I think that convergence of phones with laptops and desktops is the way of the future [4] for most people having laptops take over all functions of desktops is the best option today.

• [1] https://en.wikipedia.org/wiki/Steam_Deck
• [2] https://en.wikipedia.org/wiki/Nintendo_Switch
• [3] https://en.wikipedia.org/wiki/PlayStation_5
• [4] https://etbe.coker.com.au/2023/05/29/considering-convergence/

What is Convergence

In 2013 Kyle Rankin (at the time Linux Journal columnist and CSO of Purism) wrote a Linux Journal article about Linux convergence [1] (which means using a phone and a dock to replace a desktop) featuring the Nokia N900 smart phone and a chroot environment on the Motorola Droid 4 Android phone. Both of them have very limited hardware even by the standards of the day and neither of which were systems I’d consider using all the time. None of the Android phones I used at that time were at all comparable to any sort of desktop system I’d want to use.

Hardware for Convergence – Comparing a Phone to a Laptop

The first hardware issue for convergence is docks and other accessories to attach a small computer to hardware designed for larger computers. Laptop docks have been around for decades and for decades I haven’t been using them because they have all been expensive and specific to a particular model of laptop. Having an expensive dock at home and an expensive dock at the office and then replacing them both when the laptop is replaced may work well for some people but wasn’t something I wanted to do. The USB-C interface supports data, power, and DisplayPort video over the same cable and now USB-C docks start at about $20 on eBay and dock functionality is built in to many new monitors. I can take a USB-C device to the office of any large company and know there’s a good chance that there will be a USB-C dock ready for me to use. The fact that USB-C is a standard feature for phones gives obvious potential for convergence.

The next issue is performance. The Passmark benchmark seems like a reasonable way to compare CPUs [2]. It may not be the best benchmark but it has an excellent set of published results for Intel and AMD CPUs. I ran that benchmark on my Librem5 [3] and got a result of 507 for the CPU score. At the end of 2017 I got a Thinkpad X301 [4] which rates 678 on Passmark. So the Librem5 has 3/4 the CPU power of a laptop that was OK for my use in 2018. Given that the X301 was about the minimum specs for a PC that I can use (for things other than serious compiles, running VMs, etc) the Librem 5 has 3/4 the CPU power, only 3G of RAM compared to 6G, and 32G of storage compared to 64G. Here is the Passmark page for my Librem5 [5]. As an aside my Libnrem5 is apparently 25% faster than the other results for the same CPU – did the Purism people do something to make their device faster than most?

For me the Librem5 would be at the very low end of what I would consider a usable desktop system. A friend’s N900 (like the one Kyle used) won’t complete the Passmark test apparently due to the “Extended Instructions (NEON)” test failing. But of the rest of the tests most of them gave a result that was well below 10% of the result from the Librem5 and only the “Compression” and “CPU Single Threaded” tests managed to exceed 1/4 the speed of the Librem5. One thing to note when considering the specs of phones vs desktop systems is that the MicroSD cards designed for use in dashcams and other continuous recording devices have TBW ratings that compare well to SSDs designed for use in PCs, so swap to a MicroSD card should work reasonably well and be significantly faster than the hard disks I was using for swap in 2013!

In 2013 I was using a Thinkpad T420 as my main system [6], it had 8G of RAM (the same as my current laptop) although I noted that 4G was slow but usable at the time. Basically it seems that the Librem5 was about the sort of hardware I could have used for convergence in 2013. But by today’s standards and with the need to drive 4K monitors etc it’s not that great.

The N900 hardware specs seem very similar to the Thinkpads I was using from 1998 to about 2003. However a device for convergence will usually do more things than a laptop (IE phone and camera functionality) and software had become significantly more bloated in 1998 to 2013 time period. A Linux desktop system performed reasonably with 32MB of RAM in 1998 but by 2013 even 2G was limiting.

Software Issues for Convergence

Jeremiah Foster (Director PureOS at Purism) wrote an interesting overview of some of the software issues of convergence [7]. One of the most obvious is that the best app design for a small screen is often very different from that for a large screen. Phone apps usually have a single window that shows a view of only one part of the data that is being worked on (EG an email program that shows a list of messages or the contents of a single message but not both). Desktop apps of any complexity will either have support for multiple windows for different data (EG two messages displayed in different windows) or a single window with multiple different types of data (EG message list and a single message). What we ideally want is all the important apps to support changing modes when the active display is changed to one of a different size/resolution. The Purism people are doing some really good work in this regard. But it is a large project that needs to involve a huge range of apps.

The next thing that needs to be addressed is the OS interface for managing apps and metadata. On a phone you swipe from one part of the screen to get a list of apps while on a desktop you will probably have a small section of a large monitor reserved for showing a window list. On a desktop you will typically have an app to manage a list of items copied to the clipboard while on Android and iOS there is AFAIK no standard way to do that (there is a selection of apps in the Google Play Store to do this sort of thing).

Purism has a blog post by Sebastian Krzyszkowiak about some of the development of the OS to make it work better for convergence and the status of getting it in Debian [8].

The limitations in phone hardware force changes to the software. Software needs to use less memory because phone RAM can’t be upgraded. The OS needs to be configured for low RAM use which includes technologies like the zram kernel memory compression feature.

Security

When mobile phones first came out they were used for less secret data. Loss of a phone was annoying and expensive but not a security problem. Now phone theft for the purpose of gaining access to resources stored on the phone is becoming a known crime, here is a news report about a thief stealing credit cards and phones to receive the SMS notifications from banks [9]. We should expect that trend to continue, stealing mobile devices for ssh keys, management tools for cloud services, etc is something we should expect to happen.

A problem with mobile phones in current use is that they have one login used for all access from trivial things done in low security environments (EG paying for public transport) to sensitive things done in more secure environments (EG online banking and healthcare). Some applications take extra precautions for this EG the Android app I use for online banking requires authentication before performing any operations. The Samsung version of Android has a system called Knox for running a separate secured workspace [10]. I don’t think that the Knox approach would work well for a full Linux desktop environment, but something that provides some similar features would be a really good idea. Also running apps in containers as much as possible would be a good security feature, this is done by default in Android and desktop OSs could benefit from it.

The Linux desktop security model of logging in to a single account and getting access to everything has been outdated for a long time, probably ever since single-user Linux systems became popular. We need to change this for many reasons and convergence just makes it more urgent.

Conclusion

I have become convinced that convergence is the way of the future. It has the potential to make transporting computers easier, purchasing cheaper (buy just a phone and not buy desktop and laptop systems), and access to data more convenient. The Librem5 doesn’t seem up to the task for my use due to being slow and having short battery life, the PinePhone Pro has more powerful hardware and allegedly has better battery life [11] so it might work for my needs. The PinePhone Pro probably won’t meet the desktop computing needs of most people, but hardware keeps getting faster and cheaper so eventually most people could have their computing needs satisfied with a phone.

The current state of software for convergence and for Linux desktop security needs some improvement. I have some experience with Linux security so this is something I can help work on.

To work on improving this I asked Linux Australia for a grant for me and a friend to get PinePhone Pro devices and a selection of accessories to go with them. Having both a Librem5 and a PinePhone Pro means that I can test software in different configurations which will make developing software easier. Also having a friend who’s working on similar things will help a lot, especially as he has some low level hardware skills that I lack.

Linux Australia awarded the grant and now the PinePhones are in transit. Hopefully I will have a PinePhone in a couple of weeks to start work on this.

• [1] https://www.linuxjournal.com/content/whats-dock
• [2] https://www.passmark.com/products/pt_linux/download.php
• [3] https://etbe.coker.com.au/2022/03/19/more-librem5/
• [4] https://etbe.coker.com.au/2018/01/16/more-thinkpad-x301/
• [5] https://tinyurl.com/2jwnbgb2
• [6] https://etbe.coker.com.au/2013/10/23/thinkpad-t420/
• [7] https://tinyurl.com/yxobjae3
• [8] https://puri.sm/posts/what-is-mobile-pureos/
• [9] https://www.bbc.com/news/uk-england-london-62809151
• [10] https://en.wikipedia.org/wiki/Samsung_Knox
• [11] https://www.pine64.org/pinephonepro/

In response to my post about Android phones without Google Play [1] I received an email recommending Joplin for notes on Android [2].

Joplin supports storing notes on a number of protocols including Nextcloud and WebDAV. I setup WebDAV because it’s easiest, here is Digital Ocean instructions for WebDAV on Apache [3]. That basically works. One problem for my use case is that the Joplin client doesn’t support accounts on multiple servers and the only released way of sharing notes between accounts is using the paid Joplin Cloud service.

There is a Joplin Server in beta which allows sharing notes but that is designed to run in Docker and is written in TypeScript so it was too much pain to setup. One mitigating factor is that there are “Notebooks” which are collections of notes. So if multiple people who trust each other share an account they can have Notebooks for personal notes and a Notebook for shared notes.

There is also a Snap install of the client for Debian [4]. Snap isn’t my favourite way of doing things but packaging JavaScript programs will probably be painful so I’ll do it if I continue using Joplin.

• [1] https://etbe.coker.com.au/2022/04/20/android-without-play/
• [2] https://joplinapp.org/
• [3] https://tinyurl.com/yh8pr82j
• [4] https://snapcraft.io/install/joplin-james-carroll/debian

A while ago I was given a few reasonably high-end Android phones to give away. I gave two very nice phones to someone who looks after refugees so a couple of refugee families could make video calls to relatives. The third phone is a Huawei Nova 7i [1] which doesn’t have the Google Play Store. The Nova 7i is a ridiculously powerful computer (8G of RAM in a phone!!!) but without the Google Play Store it’s not much use to the average phone user. It has the “HuaWei App Gallery” which isn’t as bad as most of the proprietary app stores of small players in the Android world, it has SnapChat, TikTok, Telegram, Alibaba, WeChat, and Grays auction (an app I didn’t even know existed) along with many others. It also links to ApkPure (apparently a 3rd party app installer that “obtains” APK files for major commercial apps) for Facebook among others. The ApkPure thing might be Huawei outsourcing the violation of Facebook terms of service. For the moment I’ve decided to only use free software on this phone and use my old phone for non-free stuff (Facebook, LinkedIn, etc). The eventual aim is that I can only carry a phone with free software for normal use and carry a second phone if I’m active on LinkedIn or something. My recollection is that when I first got the phone (almost 2 years ago) it didn’t have such a range of apps.

The first thing to install was f-droid [2] as the app repository. F-droid has a repository of thousands of free software Android apps as well as some apps that are slightly less free which are tagged appropriately. You can install the F-Droid app from the web site. As an aside I had to go to settings and enable “force old index format” to get the list of packages, I don’t know why as other phones had worked without it.

Here are the F-Droid apps I installed:

• Kdeconnect to transfer files to PC. This has some neat features including using the PC keyboard on Android. One downside is that there’s no convenient way to kill it. I don’t want it hanging around, I want to transfer a file and close it down to minimise exposure.
• K9 is an Android app for email that I’ve used for over a decade now. Previously I’ve used it from the Play Store but it’s available in F-droid. I used Kdeconnect to transfer the exported configuration from my old phone to my PC and then from my PC to my new phone.
• I’m now using SchildiChat for Matrix as a replacement for Google Hangouts (I previously wrote about how Google is killing Hangouts [3]). One advantage of SchildiChat is that it keeps a notification running 24*7 to reduce the incidence of Android killing it. The process of sending private messages with Matrix seems noticeably slower than Hangouts, while Google will inevitably be faster than a federated system (if only because they buy better hardware than I rent) the difference shouldn’t be enough to notice (my Matrix servers might need some work).
• I used ffupdater to install Firefox. It can also install other browsers that don’t publish APK files. One of the options is “Ungoogled Chromium” which I’m not going to use even though I’ve found Google Chrome to be a great browser, I think I should go all the way in avoiding Google. There’s no description in the app of the differences between the browsers, the ffupdater web page has information about the browsers [4].
• I use Tusky for Mastodon which is a replacement for Twitter. My Mastodon address is @etbe@mastodon.nzoss.nz. Currently Mastodon needs more users, there are plenty of free servers out there and the New Zealand Open Source Society is just one I have contact with.
• I have used ConnectBot for ssh connections from Android for over 10 years, previously via the Play Store but it’s also in F-droid. To get the hash of a key from a server in the way ConnectBot displays it run “ssh-keygen -l -E md5 -f /etc/ssh/ssh_host_ed25519_key.pub“.
• I initially changed Keyboard from MS Swiftkey to the Celia keyboard that came with the phone. But it’s spelling correction was terrible, almost never suggesting words with apostrophes when appropriate and also having no apparent option to disable adult words. I’m now using OpenBoard which is a port of the Google Android keyboard which works well.
• I’ve just installed “primitive ftpd” for file transfer, it supports ftp and sftp protocols and is well written.
• I’ve installed the mpv video player which plays FullHD video at high quality using hardware decoding. I don’t need to do that sort of thing (the screen is too small to make it worth FullHD video), but it’s nice to have.
• For barcodes and QR codes I’m using Binary Eye which seems better than the Play Store one I had used previously.
• For playing music I’ve tried using the Simple Music Player (which is nice for mp3s), but it doesn’t play m4a or webm files. Auxio and Music Player Go play mp3 and m4a but not webm. So far the only programs I’ve found that can play webm are VLC and MPV, so I’m trying out VLC as a music player which it basically does but a program with the same audio features and no menu options about video would be better. Webm is important to me because I have some music videos downloaded from YouTube and webm allows me to put a binary copy of the audio data into an audio file.

Future Plans

The current main things I’m missing are a calendar, a contact list, and a shared note taking system (like Google Keep). For calendaring and a contact list the CalDAV and CardDAV protocols seem best. The most common implementation on the server side appears to be DAViCal [5]. The Nextcloud system supports CalDAV, CardDAV, web editing of notes and documents (including LibreOffice if you install that plugin) [6]. But it is huge and demands write access to all it’s own code (bad for security), and it’s not packaged for Debian. Also in my tests it gave me an error 401 when I tried to authenticate to it from the Android Nextcloud client. I’ve seen a positive review about Radicale, a simple CalDAV and CardDAV server that doesn’t need a database [7]. I prefer the Unix philosophy of keeping things simple with file storage unless there’s a real need for anything else. I don’t think that anything I ever do with calendaring will require the PostgreSQL database that DAViCal uses.

I’ll give Radicale a go for CalDAV and CardDAV, but I still need something for shared notes (shopping lists etc). Suggestions welcome.

Current Status

Lack of a contacts list is a major loss of functionality in a phone. I could store contacts in the phone memory or on the SIM, but I would still have to get all my old contacts in there and also getting something half working reduces motivation for getting it working properly. Lack of a calendar is also a problem, again I could work around that by exporting all my Google calendars as iCal URLs but I’d rather get it working correctly.

The lack of shared notes may be a harder problem to solve given the failure of Nextcloud. For that I would consider just having the keep.google.com web site always open in Mozilla at least in the short term.

At the moment I require two phones, my new Android phone without Google and the old one for my contacts list etc. Hopefully in a week or so I’ll have my new phone doing contacts, calendaring, and notes. Then my old phone will just be for proprietary apps which I don’t need most of the time and I can leave it at home when I don’t need that sort of thing.

• [1] https://en.wikipedia.org/wiki/Huawei_Nova_7i
• [2] https://f-droid.org/
• [3] https://etbe.coker.com.au/2022/03/28/hangouts-replacement/
• [4] https://notabug.org/KarlHeinz/ffupdater
• [5] https://en.wikipedia.org/wiki/DAViCal
• [6] https://en.wikipedia.org/wiki/Nextcloud
• [7] https://radicale.org/