zoom on an ipad

That may be best because I’m not really understanding what you are wanting to do.

In the app you can turn the camera on or off, audio on or off - separately or have both on at the same time. Or you can share the screen, which may or may not share the camera but still share the audio. It pretty much works the same as it does on a desktop/laptop.

I do believe if you have the zoom app you can turn off the camera part and only share audio

I’d suggest that you find a friend that has one or go to an apple store and experiment that the app will do what you want.

another way to have the camera on but no picture (which is what I think you’re asking about) would be to put a bit of a post it or other piece of paper over the lens.