I have the same issue with my iPhone XR. The rear camera and flashlight stopped working after I think 3rd or 4th developer beta. I hypothesize that this might be one of the reasons Apple ganged up on the third-party websites that were distributing developer beta profiles because someone missed this bug that's bricking the camera and they released it to the public. People like me, unfortunately, downloaded the firmware before they could've fixed it. Considering the fact that going back to iOS 15 doesn't resolve the issue and that Public Beta RC didn't fix the issue, I think the issue of this magnitude would result in many people losing their rear camera and having to pay for the repair.