I’ve experienced some of this funny business in the past myself …
Are you logging into the GUI session immediately upon being presented the login screen? One thing you can try is to wait something like 30(?) seconds before logging into the GUI session and see if you still have the weirdness going on.
If devices show up as expected, I’d wager to say that this the result of some race condition with sys-usb. You can play around with memory settings and other bits but, this is likely stemming from the use of the bloated “full” template as opposed to a minimal template for sys-usb. I’m fully aware that there is no other option available during initial initial and, would love to see minimal templates included in the official ISO in the future as, I see so many issues posted that are easily remedied by leveraging minimal templates for service qubes. Not to mention that the default use of the “full” templates is unnecessarily glowie IMO.
It may seem like a bit much and, may not work straight away but, you can find some steps to rebuild sys-usb with a minimal template here. Read it over a couple times to understand the flow/logic as, the steps were offered from memory and, there might be a feeling of frustrated disappointment if things don’t work out immediately but, rebuilding service qubes based on minimal templates ought to alleviate many issues/problems/errors. YMMV