Webcam not working in Ubuntu 19.10 on XPS 13 [9343]
Solution 1:
This probably isn't the solution to your problem, but I'll post it here anyway in case it helps someone else.
I have an XPS 13 9343 with Ubuntu 20.04, and the integrated webcam wasn't detected. Turned out I had to enable it in UEFI.
(Note that it had worked before, and I did not actively disabled it.)