I was a backer of Elite and have it in my Steam account, I think you have to go to the Elite website and ask for a key but it's a while since I added mine so might not be possible anymore.
I have one of these - Logitech K400 Plus Not using it on a steamdeck but with my PC in the games room. 6 years now and it's still working fine, probably changed the battery once and it's been chucked around all over the shop, stood on, dropped etc.
