did you ever try it with such a real low bandwidth connection? I somehow doubt that it's really that nice to transmit WQHD desktops as is... Also I don't really get the thing about a 30 person, all hands video-conference. The only thing coming out of that (on the average 1080p screen) is gratifying the host: "all these people show up, because of meeee" (and yeah, school kids could do whatever they want in an audio conference. but kids can do that also with zoom (unless you are spying on them with the integrated spyware...) and they also can sit through one session and then replay their face all the time...

How does "P2P can't even maintain audio for large-ish groups in my experience" translate to "transmitting WQHD desktops"?

One of the large strengths of tools like Zoom over the typical WebRTC-P2P thing is that they can avoid exactly that, and e.g. maintain a stable audio only (or extremely low-quality video) conference for people on slow connections.

I suppose you can stop transmission of all video in jitsi as well (or at least it should be possible, given that it supports landline dial-in as well)? low quality video of heads is not that interesting for me personally (and for all purposes except keeping a literal headcount).

Jitsi is not an example of a peer-to-peer system for group calls. The default UI doesn't expose that many configuration options for this sadly from what I've heard.