I'm looking for video chat software similar to Zoom, that works on at least Windows, iOS and Android, and ideally Linux as well. (A browser solution would be okay if it works reliably across browsers and operating systems.) The key feature I'm interested in is what I'm calling (for lack of a better term) "asymmetric rooms". What I mean by this is that the host can talk to all participants, but each participant can talk only to the host --- the non-host participants can't see or interact with one another.
I'm interested in this for organizing "classes" that are sort of like office hours or drop-in tutoring, where each participant is there to interact with the host. In this situation, having all participants see and hear the video/audio is distracting since most of it is about other people's issues that aren't germane to their own. Also, it's nicer for privacy if participants don't interact with one another. At the same time, since the interaction with any given participant is often short, it's convenient to be able to give everyone the same room URL/number to drop in, rather than having to schedule separate meetings for each individual, or manage a "waiting room" or "breakout rooms" by manually shunting participants into separate rooms. (Also, apparently Zoom's breakout rooms can't be managed when the host is using Android or iOS.)
It would also be great if the software supported other features like Zoom, such as screen sharing and a shared whiteboard.