Also, looking at old kernel logs from back when it was working would be useful (/var/log/kernel.N.gz where N if the biggest number there is). Hopefully that will show what device is on usb 1-5 (though I believe port numbers may change over time and depend on what's plugged in).
That was the perfect piece of advice. I found the exact log where the issue began: 2023-01-06T20:20:28.225698-08:00 cockpit kernel: [ 25.515977] usb 1-5: Failed to suspend device, error -110 Coincidentally, this is also exactly when the bluetooth on my motherboard stopped working. (The WiFi is on the same MT7921K chipset and still works weirdly). Can you suggest any steps other than straight-up RMA'ing the mobo? (That might fix the USB-C as well, heh.) Matthew