Maybe my definition of hotplug is different.
Using HDMI did not require touching sys-usb, though I have also used this once, today.
Anything which is plugged in to USB ports shows up in sys-usb.
From there I can attach it to other Qubes, with the challenges I mentioned of Android and camera.
I have not had to reboot, with the exception of the camera.
I have not compiled my own kernels for Qubes. While I used to compile kernels for various Debian releases, I’m happy not to do that now, and I haven’t done it for Qubes yet.
I wonder whether problems with the camera is due to there being 2 USB controllers, one on CPU, the other on motherboard, which is mentioned below