Are there stable open source apps that would work well for conferencing, larger meetings or teaching?
Solution 1:
BigBlueButton is a stable and useful teaching platform, however, it is not peer to peer. It's a web-based app that runs on a server and has very specific software system requirements. There are several companies that host installations for educational institutions.
It's got whiteboard and slides support. Unlike teams, it works just as well with Libre Office. Unlike Zoom, it doesn't require anyone to install special software.
Routing system sound through it, however, is slightly fiddly.