I just stumbled across SELinux as an additional security measure on CentOS 7 (or 8) and wondered if it would be meaningful to enable it. I searched here in the forum for SELinux and didn't find a single entry, which makes me think that it isn't used. Or it works so well that there is no reason to ask ever. However, I find at other places positive as well as negative opinions about it, and as it is claimed to help improve security, it might be worth considering. But the negative opinions relate to experiences where SELinux made some functions stop working, which I (and probably anybody) don't want. It would be nice to hear from other users if they have any experience, good or bad, and maybe even suggestions.
It will make your server stop working, see perfect server guides, which tell you that you must disable it if you want to use ISPConfig on that server. If you would want to use SELinux, you will have to write SELinux rules for all services and probably for each website that you add in ISPConfig to make it work.
Some discussion at https://git.ispconfig.org/ispconfig/ispconfig3/-/issues/2840 and https://git.ispconfig.org/ispconfig/ispconfig3/-/issues/5617
