I’ve been gaming on Linux primarily for the last ~5 years. I also use Linux professionally (though I am a research scientist, not a programmer). I would say Linux gaming is 95% feasible if you do SP only. If you do MP in addition to SP, it’s maybe 70% ish doable? If you do just MP, that drops to like 20%-30%.
Most things “just work” now, especially for SP games. Occasionally you find an old game with a glitch or bug you need to search the web to fix, but it’s not bad, similar things happen on Windows.
If you stick to the biggest supported distros (Fedora, Ubuntu) and stick to Steam, and stick to SP, it’s basically no different from Windows as far as ease of use and compatibility.
Sort of. I host a Matrix Synapse server for about 15 friends. Some of them use rooms on the big Matrix.org server as well, some bridge to Discord and Facebook, and some chat with other smaller groups. By default, Synapse won’t sync rooms you haven’t joined. It also won’t copy files - it’ll fetch those I believe (although maybe it’ll keep a few days worth of files around?).
After about 5 years of hosting it, we’re sitting at 90GB total disc space used, of which ~70GB is the database. You can compress the database and save lots of disc space (50%+) but I haven’t gotten around to that yet.