TLDR: The r/selfhosted subreddit has a Discord server. The owner’s account got hacked leaving the server in a precarious state. They submitted a support ticket, but Discord has not taken action in weeks and probably won’t at all, so they are considering starting a new Discord server.
Stoat chat has been a good Discord alternative.
What advantage does it have compared to Matrix?/IRC?
It’s worked okay for me so far as well. The mobile apps aren’t super stable yet and notifications don’t work but it works for what it is right now. I do miss the stability of discord but I’m not going back