While troubleshooting a mouse/keyboard problem with the KVM I have connected to my Allonis Shelf unit I wanted to be able to use the front panel USB ports of the Shelf unit while testing. I found a note in the DeskPi web documentation about enabling the front panel USB ports. I added the following to /boot/firmware/config.txt
# Enable front USB ports
dtoverlay=dwc2,dr_mode=host
After a reboot I was able to use the front panel USB ports for mouse and keyboard access.