Over on JupyterLite, we’ve added an (incomplete) replacement for the built-in, jupyter_server-based collaboration provider that calls out to a y-webrtc host (presently hard-coded to the demo one). Theoretically, someone who had the need for it would be able to turn that into a standalone extension, install it in every lab, and run the underlying nodejs server as a hub service so it would at least be “inside the wire,” as this is going to spam all yer data.
There are a number of other existing connectors, that might work as well: the y-xmpp one, backed by an ejabberd instance, would probably scale to ridiculous levels.