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.