Mostly, it's the must-have Indie darlings, with a sprinkling of AAA fodder.
I've loved:
Rimworld
Yakuza 0
Slay The Spire
Dave the Diver
Dredge
I've found that I enjoy playing offbeat adventure games on the deck more than I did sat at a PC. Detention, Norco, Loretta, To The Moon, that sort of thing is perfect for playing in bed, propped against the pillows.
I'm personally a huge fan of project zomboid, though I had to tweak the controls a little to make it work well.
I'm sure Stardew Valley is a perfect match for the deck, but I've played it too much already.