So what do we learn with all theses traces:
Linux Mint uses a recent 5.4 kernel.
But your qubes use an old 4.19 kernel (it’s the default Qubes OS kernel).
Your webcam is here with the device id 046d:085c.
On Qubes OS, your webcam is viewable in dom0 (same device id as Linux Mint). But the kernel doesn’t recognize it as a C922 Pro Stream Webcam (like Linux Mint does). This means your Qubes-OS kernel doesn’t include the driver for your webcam.
Conclusion: you should update your Qubes OS kernel.
How to do this? Carefully read the kernel-upgrade, you should install the kernel-latest in dom0. But you can keep the 4.19 kernel as the default kernel for dom0 (i.e. don’t edit /boot/efi/EFI/qubes/xen.cfg). Reboot Qubes OS. You will use the kernel-latest on the VM that will manage your webcam (see below).
Then you should choose on which VM attach your webcam, read usb-devices. I don’t know webcam on Qubes OS, maybe your webcam should be attached to sys-usb or to your standalone VM videoconferences, get advices from skilled people who already answered on this thread. Next switch the choosed VM to kernel-latest (process: Qubes Manager > right clic on the VM > Qube Settings > Advanced tab > in the Kernel field choose the 5.x kernel), then restart the VM. In this VM, lsusb should now display the webcam with its name (like Linux Mint does).
Then check your webcam works with the Cheese program as suggested on top of this thread.
Hope this will work!
I’m surprised by these last traces, because the kernel recognize your webcam and load the uvcvideo driver. Did you really do it on dom0 as requested or on Linux Mint?