I'm unclear what subset of users are desktop only Zoom users that aren't also familiar with the same "Do you want to allow this app to access your camera/microphone?" dialogs on mobile devices. This can't be a large demographic, can it?
If only there was some happy middle ground between never asking and always asking ...
I'd be totally fine with default-on voip sound - with a red, muted mic button and a bubble saying 'tap to unmute'.