Just add an empty mapping for it in gamecontrollerdb.txt.
For Moonlight from Flathub and my version of the Azeron Keypad, this is as simple as this command:
echo '03000000d0160000bc10000011010000,LTD Azeron Keypad,platform:Linux,' >> "$HOME/.var/app/com.moonlight_stream.Moonlight/cache/Moonlight Game Streaming Project/Moonlight/gamecontrollerdb.txt"
This file might get overridden on updates though...
So to bypass this, we put that change into a wrapper script (ensure it's executable with chmod +x).