Gentoo has binary packages now, you might want to try it again. There are retroarch packages in the overlays. Otherwise, interesting distros I know of that you haven't listed yet are
- Void
- Guix System
- Gobo Linux (unfortunately very low on maintainers so probably not usable as a daily driver, but it is to me the most interesting of these)
Personally I'd go with Signal. Matrix has a certain jank level IME, for example rooms can get desynced between homeservers and the only way to fix is to create a new room and abandon the old one. Not sure how often that happens for small scale use though, I've only seen it in large rooms.