Just noticed a new feature in (I think) the latest update of OBS. It lets you "Start Virtual Camera" just like you would "Start Streaming". Then in Zoom or Google Meet, you can select that virtual camera feed as your camera. Also just realized that this could be the next Zoombombing technique - you've prevented people from sharing their screen, but now they can just use OBS to send their screen to Zoom, etc. Aargh!