Stoat (formerly known as Revolt) is a selfhostable, FOSS replacement for discord [Group chats and voice channels you can join any time].
Cool new name, however not as easy to use in other languages.
Voice chat is stil not officialy implemented.
Self-hosting there. Apparently nothing to do for you if you had already hosted before the name change.
The Android app has unfortunately disappeared (not been updated) on F-droid.
Edit: added short description for clarification
i honestly think that if revolt had federation, then it would be the obvious choice for me, but alas. personally i’m still hopeful for polyproto getting off the ground, but the boring realistic choice for the time being is probably something like XMPP + mumble
It looks like polyproto doesn’t have any intent to implement voice chat or screen sharing?
i think for my purposes i’m fine with hosting that through a separate service, so instead of XMPP + mumble i would run polyproto + mumble (or some other voip solution, screen sharing seems to be a decent way away in mumble)
but (as i understand it), polyproto isn’t a chat protocol per se, but more a protocol for federated message authentication. as an application of this protocol, they’re building polyproto-chat, which is a chat protocol. in theory, one could then also build a polyproto-voice so you can use the same account for both chatting and voice calls. i still think this is pretty far away, considering how young polyproto is, which is why my current vision is chat and voice as two separate services (which i also prefer because i imagine it makes the technology simpler and hosting easier)