I mostly use mine when traveling so currently working on God of War II on the PS2 since i finished the first one recently on the Deck. I have Jak and Daxter and Sly Cooper queued up for later since I never got around to playing those before.
Edit: For Elden Ring bleed has really helped me on harder enemies. That and finding some good farming spots.
I have looked into this myself recently. Still a few blockers for me, one of the big ones being VR. The Steam Deck and its OS have really pushed gaming forward on Linux though.