Regarding the warning for the fdroid app that was recommended by an other user, it might be ok if you place a clock with second-display in the view, so that you know if it has frozen.

Maybe a jitsi meet room with webcam would do. When doing it with a computer instead of a phone, you can set up OBS virtual camera (1 click thing) to add a filter that makes it grayscale, but that's slightly more clicks.