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 looked at the website and every link and have no idea what it does.
“Connect with your friends and community” was in a screenshot.
Ah! If you have never heard of it I can tell you: it’s the foss, self-hostable equivalent of Discord. Except we are still waiting for the voice channels.
If there’s no voice channels, then why reinvent IRC?
There’s a wide gap of stuff one can do between IRC and “chat with voice channels”. For example, having a better protocol with better formatting options, a moderation API, better account management, other forms of multimedia (page embeds, images).
Compared to some other alternatives, I think the thing it really has going for it is how simple it is. It’s really a drop in replacement for discord, something I actually think maybe my friends that don’t really care about Foss would consider switching to. They’ve told me they don’t want to take the time to learn a new messaging software, I don’t think they’d have to with this.
Syntax highlighting for code blocks is the reason I prefer discord over slack for collaborating and just chatting with friends who know how to code. I imagine some irc clients exist that so the same, but at least with discord I know my recipient is guaranteed to see what I see.