Its looking like Microsoft is gonna buy Discord. Preferably open source, and has a big userbase, and has Windows and Linux option. (but mainly windows because i only game on windows now.)
Matrix
Not really a Discord alternative until they ship voice channels. Revolt chat is a straight up Discord clone, but it’s not federated, they have really obfuscated the way to self host it, and their releases are way older than what the main server is running. Plus, it’s developed by kids who don’t give a crap about anything.
So, Matrix is the best chat out there, but it’s not a Discord alternative.
I know my position and the advocacy that I do, but realistically Discord has no replacements if you are looking on the aspect of available users and communities. Technicalities matter only so much, no matter the other alternatives like rocket.chat or Mumble.
If you can get around learning and practicing OPSEC, like me, simply do not type self doxxing PII, have a constant common typing grammar pattern and not share images or media without stripped metadata. It is plenty to obtain decent anonymity by obscurity, and decent amount of privacy. Use Discord as a resource tool rather than shitposting all day, and you are good. This is my personal way of usage.