I haven’t hosted my own matrix server yet. is it safe to join an instance? I don’t really know how private that would be. the question is when I signup/login would I be giving out my IP? is the metadata private? sorry for asking this, I’m just a bit paranoid
XMPP does calls as well: https://blog.wirelessmoves.com/2020/05/xmpp-voice-and-video-calls-with-conversations-a-dream-come-true.html
You could also combine an XMPP server you manage with something like Asterisk to then allow your XMPP clients to do SIP calls through that, though that is a bit involved.
The XMPP calls are set in Jingle XEPs. AFAIK, there are big stability issues even with the XEPs for STUN/TURN discovery.
Your experience may vary, but on my personal XMPP server with it’s own STUN/TURN server using conversations.im - calls pretty much Just Work (edit: I’ve only tried a call with a siskin client outside of conversations and that worked too).