Anything turn-based, especially mouse-driven titles. Slay the Spire, Chess, Riichi Mahjong, Balatro, etc.

Puyo Puyo Champions has a one-handed preset in its controller options. Do note that if you want to play online, only Switch is active since that's where Japan is, I can't recommend the game on other platforms.

Kirby Air Ride uses only one button + analog stick, and any button works, so you can use L. Would have to be left hand for the original, but the sequel coming out later this month has a detailed accessibility menu, which I bet will include right-handed settings.

Crypt of the Necrodancer is designed to be playable with just four arrows, in case anyone wanted to play it on a DDR mat. Which also means you can play with arrow keys or WASD.

Rhythm Doctor is actually just one button.

Rhythm Heaven Fever uses only A and B. Rhythm Heaven DS uses only stylus. The rest of the series uses d-pad as well though, so those are less playable.

Come to think of it, any DS game that only uses stylus.