u/Cunning-Etrean

oh I found it, it was a bug indeed. ty
Bug #1978416 “External USB webcam is not working” : Bugs : linux-signed-hwe-5.13 package : Ubuntu

Thanks! I'm not trying to file an official bug report yet. I'm looking for troubleshooting advice because I'm not sure whether this is a kernel regression, a UVC driver issue, or a USB compatibility problem. The webcam works perfectly on Windows, but on Ubuntu it produces UVC probe/commit timeouts and streaming I/O errors. Plugging it in also causes system slowdowns and my headphones to repeatedly mute and unmute. Unplugging it immediately restores normal behaviour. I'd appreciate advice on what to investigate before considering a kernel change.