Games

You might have some luck with a controller, using only a half of it, and re-mapping all controls there. Steam Controller might be great since it has touchpads. That might make some mouse-requiring games playable.

Using only keyboard, damn that's difficult to find something, haha. I think these might work, just going by my memory: FTL, Toki Tori, Undertale, VVVVVV, Braid, Dome Keeper. Basically that kind of simple 2D games. Then almost any racing game.

You could also try some eye tracking solution, can't help with that though.

Do you like rpg card games? It's on my android but tavern rumble has been super fun for me recently. I wonder if you can find it on pc

Runescape

Dang. Would have recommended One Finger Death Punch as it can be played with only one finger but the whole game is essentially QTEs. xD

Maybe some point and click adventure games? Those tend to have great stories. The Longest Journey, Syberia, stuff like that.

FFXIV can be played with just a mouse. Free to level 60 (mmo)RPG with good story telling. But using the mouse in your left hand might feel strange tbf.

The Curse of the Golden Idol is a detective-puzzle game that is easily played one handed, is cheap, and is great.

Invisible Inc is like a stealthy XCOM (which I see on your profile), and again, easily played one handed.

If you're willing to bend on the RTS thing, Tooth and Tail is an RTS game that is almost completely played with your left hand in keyboard mode - it's an RTS designed for gamepads so it only uses wasd and like 6 action buttons (rally selected, rally all, cycle selection forward, cycle back, build, sell). It uses the mouse buttons to click for the rally commands but not the pointing by default, you could rebind the mouse click rally commands to like lshift and ctrl or something like that and it should work well. But the single player campaign does get difficult towards the halfway mark

If you have a tablet or a large phone, maybe board games? Some boardgame apps have excellent campaign modes. My go to for this is Galaxy Trucker, but it has a time pressure component.

Anything that is turn-based will work really, or doesn't rely on a real-time mechanic.

I do suggest looking at a small trackball that you can use in the meantime. It'll be useful for the times when you need a pointing device in a smaller space, for whatever reason.

Racing games in general, personally I like Forza Horizon 5, you could play it with WASD and a spacebar

Darkest dungeon dungeon should be playable with only one hand available.

Civ V/Civ VI can all be played entirely with a mouse. Very fun, too.

Civ

Civ 5

FTL: Faster Than Light, an incredible rouge-like in space

Pros:

• All actions have a leyboard shortcut

• you can pause anytime and plan ahead

• will satisfy your analytical brain that needs puzzles

• randomized, each game will be different

• can be played in short bursts should you get tired with the cast or whatever on

• is amazing

• randomized

• dirt cheap

Cons:

• you still need to use the mouse to aim weapons, albeit no need to be ultra precise...most of the time
• randomized...will punish you sometimes so you just have to take it on the chin. Part of the fun and all that.