I’m seeing this same issue. I was about to reset my entire deck.
Out of interest, if you reboot your deck with a device plugged in are you able to see the USB device?
I noticed, that my mouse works until I unplug it, same for a USB stick. I can use it just fine while it’s working too.
I think I solved my issues…
I created a thumb drive with the recovery image using my PC. I rebooted the deck with the USB plugged in, I booted in to the recovery desktop and just reinstalled SteamDeck OS only (the one that attempts to keep your games installed). After it restarted it is now allowing me to plug and unplug USB devices ok. Tested with a thumb drive and a USB SSD.