[Pxtl]

For the audio side, Mumble is okay. Doesn't do feedback cancellation as well as Zoom, and it uses keys to auth which are really confusing for the user (and the UI isn't great at letting you switch which you're using).

But I got a mumble server up and running in no time flat, so it works that way, and the audio quality is amazing - far better than Zoom - as long as everybody's wearing properly-configured headsets.