This is going around in circles.
Since your camera doesn't work in both your main and test accounts, it's got to be a system problem, so I suggest that since nothing else has worked, it's last resort, i.e. nuke & pave, time.
Boot from your clone, erase your internal drive, install Catalina from scratch, and import your settings from your clone with Migration Assistant, and if that doesn't get your camera working, it will establish that your problem is hardware, rather than software, based.
