Recently a user has been asking about SE Linux support in MEPIS . He seems to expect that as the distribution is based on Debian it should have the same SE Linux support as is in Debian.
The problem with derived distributions (which potentially applies to all variants of Debian, Fedora, and RHEL) is that the compilation options used may differ from what is required for SE Linux support.
If an application works in Debian then you can expect that it will work in all derived distributions. But SE Linux is not an application, it is a security extension to the OS which includes code in the kernel, login, cron, pam, sshd, logrotate, and others. For any one of these packages a maintainer of a derived distribution might decide to turn off features to save disk space or memory, or because they want to use features which don’t work well with them (due to functional differences or bugs). The maintainer of a derived distribution might even decide that they just don’t like a feature and disable it for that reason alone!
I believe that it is possible to use APT with multiple repositories and specify preferences for each repository. So it should be possible to use a source such as MEPIS for most packages but Debian (or my private repository of SE Linux back-ports ) for the packages which need SE Linux support.
That said, I am not sure why someone would want to use MEPIS with SE Linux. Currently the benefits of SE Linux are of most use for a server and MEPIS is a desktop focussed distribution. Debian works reasonably well for a desktop (it has worked well for me for most of the past 11 years), so it seems that Debian for a SE Linux desktop machine is a good choice and Debian is a better choice than MEPIS for a server.