Idk if you can get these to work on the deck; they are not all sold on Steam and I don't know how well they play with Linux, but here's some to at least look into:
Planescape: Torment
Icewind Dale 1 & 2
Baldur's Gate 1 & 2 (and 3 for that matter, which does for sure work on the deck)
Fallout 1 & 2
Neverwinter Nights (particularly its two big expansions)
feels too much like D&D
Well... Fuck. If you didn't even like Disco Elysium there is no hope... π© All of these are literally D&D games except Fallout, which was based on GURPS.