Steam Deck - Second Controller never works?

Hi, I’m having a weird issue that is isolated to Steamdeck.

It’s a local two-player game in 5.3.1, using two controllers set up with the new Enhanced Input system. Overall I think this part is pretty standard, as both controllers work on PC in editor and on a Windows packaged build without any issue - I have sanity checked myself by going through a few tutorials and it seems that everyone is using it the same way I am.

When launched on SteamDeck, either through packaging a Linux build and using the SteamdOS Devkit Client, or launching directly from UE5 with my Deck plugged in - the second character never gets any input.

This is regardless of how many controllers I have plugged in, or what input order they are set to on the Deck, the second player just never reacts - I have no clue why?

Another Note, “Skip Assigning Gamepad to Player 1” in Project Settings also does nothing on both PC and Deck, although I assume this is something to do with the new input system.

Any help would be appreciated!