As for “why is it hard to self-host”, it is only NAT traversal.

TURN, STUN, ICE, etc. are not fun to debug. Not sure if anyone still bothers fiddling with TOS/DSCP on their router. You could build a server that just exposes a TCP port and call it a day, but this gets you latency. Corporate firewalls lovhttps://piefed.social/c/selfhosted/p/1772277/why-is-self-hosted-voice-chat-so-hard#e to randomly block some UDP port ranges but not others.