I highly recommend Caves of Qud. It's great for keyboard-only. I think it's got controller support too. The game is very confusing at first, but once you get the hang of it you can really get sucked in. Runs great on ubuntu.
Though if they play Caves of Qud, I'd recommend playing in either Roleplay mode (which enables autosave checkpoints at settlements) or Wander mode (where most enemies in the game start off neutral to you, and you gain XP by exploring rather than fighting). Classic mode would be intolerable for anyone but a hardcore gamer.