XCom

Or I guess anything with keyboard/mouse.

if they are still active the mmo's champions online and star trek online are tab targeting and even allow for some scripting. I actually had posted on reddit that I would like for people with disabilities to know about them. the right builds can be done with input every so often that does not need to be split second (some roles do require a bit more timing but if its just one handed its toatlly doable)

Try Neo Scavenger if you like things like Zomboid

Chess on lichess

Pokémon Let’s Go [Eevee / Pikachu] can be played with a single joycon vertical in one hand. They designed it to be played with their Pokéball controller, accidentally making it super accessible.

Baldur's gate 3 is totally playable with 1 hand.

Return of the Obra Dinn and the golden idol games would probably work. I think you could do everything with mouse clicks or hitting a few keys with your good hand, nothing is time based. Other puzzle based games might work too (lorelai and the laser eye, Blue Prince?)

Mostly 2D factory games, like Factorio could also be doable. Would be a little annoying, but it would work.

Balatro, Dwarf Fortress/Rimworld, pokerogue

Mixing a batch.

A little 5 on 1.

distributing free literature

If you can still use a mouse well, grand strategy games can be played with one hand. Despite all the (deserved) criticism they get, paradox games are a lot of fun. (and their modern ones even feel like a full game without having to buy any dlc) They can be a bit difficult to keep up with without a keyboard though so play on lower speeds.

If you are more concious about who you give your money to, endless legend 2 is a 4x published by hooded horse that is very good (think civ but fantasy) and since it is turn based it is a lot easier to play with just a mouse.

Sins of a Solar Empire. It's a space based strategy game that I've sunk hours into. years ago I used to have really shotty internet so it would go down all the time. I'd play that game for 8 hours a pop easily and the time would just fly by. I'm not even a big strategy gamer but I adored that game.

Dwarf fortress, chess, crosswords, Nonograms, sudoku

Check out scummVM and ROMs for old point and click adventure games like grim fandango, monkey island, Sam & max, etc

Civilization 7 only requires one hand using a mouse, which includes the Switch 2.

You can probably play Vampire Survivors. All you really do is move around.

Obligatory Dwarf Fortress

I hear pocket pool is a lot of fun.

Any points and click adventure game, there are loads including old classics and modern good games.

Monkey Island remasters are fun and can be played with mouse. Broken Sword games are also good.

Rusty Lake games are great if you prefer more puzzle games than narrative ones. Still has a great somewhat surreal plot just not like a point and click narrative game.

Also If you havent played dwarf fortress now is the time to learn, the siege update came out this week. Mouse or keyboard, or both, but definitely can be done one handed.

Vampire Survivor that others have suggested is a good shout, one hand on the keyboard is enough and its very addictive.

Balatro and Into The Breach

Monument Valley 1, 2, and 3 (mobile games). An interesting set of puzzle games with good visuals. They only require single taps to work.

Also can get a mouse for the Steam Deck (or a PC if you have one). There are a lot of good games that you can likely use with a mouse if the hand/wrist motion doesn't cause pain or discomfort for your thumb.

Might not be in your library, but mouse only game I've been enjoying is beat cop.

80s love letter to cop games, in the style of papers please. Reviews are a little mixed, it is a particular game, and it's 80s warts and all. On sale currently.

https://store.steampowered.com/app/461950/Beat_Cop/

Turn-based?

Does this actually get in the way when you're playing with mouse and keyboard? I do use my non-dominant thumb for hitting the space, alt and strg keys, but in many games that's kinda optional, especially when the games aren't super challenging. Turn-based RPGs like Divinity: Original Sin or Baldur's Gate 3 should work great.

Fruit Ninja comes to mind.

Have you considered pocket ball?

Have you considered vampire survivors? That’s a fun one on iOS and android.

Which thumb? If your left thumb is still functional, when I had a hand injury in middle school, I got to be really good at Super Monkey Ball 1 and 2. If your dominant/mouse hand is still functional, anything mouse-driven ought to do, and that covers a wide range of genres from CRPGs to adventure games to 4X games and more.