According to the folks in #media, this sort of thing should probably be a release blocker.
Hey astevenson, just getting this on your radar. The solution that the folks in #media suggested was that we uplift a patch to Beta (71) that disables the PiP toggle and context menu item for videos that have
srcObject !== null on it.
This means that for 71, PiP would not be available for the types of <video> elements that are receiving, for example, streams from the camera, the desktop, or any other type of MediaStream. Normal videos, like the ones on YouTube, Twitch, Amazon, Netflix, etc, will be unaffected.
We would then work to fix this bug, hopefully for 72, and re-enable the PiP toggle and context menus for that kind of <video> element.
This seemed like the least riskiest option for 71. Does that sound satisfactory?
Edit: Updated because I got the version numbers wrong.