Comment 33 for bug 1956461

I believe this bug was caused by this commit in the kernel:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/sound/usb/quirks-table.h?id=48827e1d6af58f219e89c7ec08dccbca28c7694e

A patch to fix the issue was committed to the kernel 11 days ago:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/sound/usb/quirks-table.h?id=4ee02e20893d2f9e951c7888f2284fa608ddaa35

It appears that the problem is that after the buggy original patch, the snd-usb-audio module takes over the entire webcam and prevents the uvcvideo driver from accessing it. No idea how long it will take Ubuntu to bring this patch into their kernels. In the meantime, I'm assuming you could work around it by doing something like this (with the webcam plugged in) to force the uvcvideo driver to load first:

sudo modprobe -r snd_usb_audio
sudo modprobe -r uvcvideo
sudo modprobe uvcvideo
sudo modprobe snd_usb_audio

(Edit: corrected name of snd_usb_audio, thanks Attila!)