I own this game on Origin. First downloaded the EA App and installed on Desktop mode but it only worked for a few hours. I then followed a reddit guide for installing origin and setting up the game as shortcuts in steam. Everything working fine now.

I have tried a lot of different controller settings. These worked best for me:

• Right trackpad mouse, left trackpad radial menü with numbers 1-0 (skills, dialog choices )
• Right stick as mouse (but with touch = right mouseclick -> easy camera control)
• Left stick as wqse (works as wasd should)
• ABXY Buttons with important actions (e.g. Jump, Use, Scan environment, etc) and some other actions bound to double press (potion, switch target)
• Grip Buttons as 1-4 for skills mainly

Guide on Reddit: https://www.reddit.com/r/SteamDeck/comments/tx6srv/guide_installing_origin_on_the_steam_deck_the/