If all else fails, Vampire Survivors.

Slay the Spire and Monster Train are great singleplayer card games that can be played with just the mouse.

Pretty much any turn based RPG is on the table, I can easily recommend Octopath Traveler 2.

You can also play story-driven games like Telltale games and Pheonix Wright, those are pretty fun.

The recently released Baldur’s Gate 3 can be played with one hand perfectly fine. Your arm will likely heal before you finish it.

Edit: just noticed that you said you want keyboard only, in which case BG3 might not be ideal since it’s mostly mouse based. I think you can customize it to play with keyboard only since it has gamepad support, but don’t know what that’d be like.

There’s no fast paced clicking required though, so you could try to adapt to left handed mousery if you really want to play that one.

Baldurs gate 3

Peglin is fun and can be done with one hand. You have to like peggle kind of games. It's in early access, but to me it's already complete.

Coromon is like classic Pokemon but has some really cool little tricks up it's sleeve.

Rise of the third power is kinda like final fantasy. Lots of great story telling and music.

Halcyon 6. It's a spoof off of space games except it's in rpg form. Used references from a lot of space series. Most startreck.

Into the breach is a great game.

All of these are indie games that I really enjoyed.

I played through 'One Finger Death Punch" with a broken arm.

Would recommend.

Almost Any visual novel.

Crypt of the NecroDancer can be played with one hand. Inputs are timed (due to it being a rhythm game), but you should be fine because the only inputs are WASD (or arrow keys if you prefer). It's a roguelike, so there's not much in the way of storytelling and it's pretty challenging, but I feel like the gameplay is pretty puzzle-esque. If it's any argument, I'm a huge fan of puzzles and I really enjoyed NecroDancer

Some of the best old school turn based RPGs are on sale at Humble Bundle at the momemnt. Those should be playable with a broken arm. Get well soon!

It's easy to overlook because of the graphics, but Caves of Qud is a really interesting game that fits your criteria.

It's hard to explain just what it really is or what makes it great, but it has a good mixture of generated and written content that keeps it interesting.

Baulders Gate 3 is prettt mouse heavy. Dont need to use the keyboard much at all. You can also set the screen to scroll with the mouse.

Not to mention its the biggest game out now

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.

Baba is You

Dead or Alive Beach Volleyball Xtreme 3

Caves of Qud is a really neat turn based roguelike that kinda focuses on exploration. It's a bit hard to get into but if you do it's really neat. Very very keyboard friendly, its my go-to game on my laptop.

It has difficulty modes that are... Less hard lol

If you are into VR, Beat Saber has some one-handed songs and Pistol Whip is mostly one-handed. The exercise of playing those games improves overall circulation which helps the healing of fractures.

Oh god I know too much about this. Long comment. Sadlol.

What kind of cast? Above or below the elbow?

I had above the elbow for 9 weeks once and below 3 times for 3-6 weeks on my right arm. Only below the elbow on my left but 5 times. My bones aren’t so good.

Above the elbow I played a lot of Warcraft 3(long time ago lol), Civ, AoE etc. Games that only required simple clicking but lots of hot keys to control. Above the elbow cast prevents a lot of you ability to rotate your arm so switching the mouse to your left doesn’t help much.

Below the elbow it depends if your thumb is immobile or not. If your thumb is free then it’s a matter of buying a cheap small mouse that will fit in your palm with the giant cast bulge. FPS and fast movements will be painful and not recommended but slower games and general use isn’t much impeded.

Immobile thumb is maybe the worst. Grab a cheap number pad and place it under your hand so you can use four fingers on the buttons. Mouse in your left hand. This severely limits what you can do with a computer.

Look up some brain exercises to ease the transition between sides of your brain and handedness. Also hold on to the skills you develop in these few weeks. Being able to work right or left hand helps with a lot of manual tasks with weird angles like using a drill under a sink or what have you.

I know you said your right arm is broken, but The 7th Guest (and the sequel, The 11th Hour, but the puzzles are very difficult) would be easy to play with your off-hand mouse anyways

just make sure you use ScummVM for them, because the versions that Steam/GOG are selling aren't very stable

similarly, the first 3 Monkey Island games, or Myst/Riven

Slay the Spire and Darkest Dungeon can be played with only a mouse and you don't need any reaction, maybe when you configure the overlay in the settings for the games it's then playable with only the keybord. Maybe you can also play Dredge in the passive mode with only one hand and only keybord I havent tried it out with this restriction

Cannot view the link without signing in, but Peglin can be played with just the arrow keys and space bar as the minimum amount of keys needed. I cannot say whether WASD works, but it's pretty simple to play.

XCOM and Shadowrun returns! Just use the mouse with the other hand. Both games give you all the time you need. Battletech is a goog one handed game, too.

Darkest Dungeon is all about the mouse.

One Finger Death Punch

I recommend playing the final fantasy games in order. Most of the older ones are only the dpad and two buttons.

Vampire Survivors?

Are you sure it has to be keyboard-only? Would a mouse or cheap touchpad work with your off hand, so long as the games don't require fast response or fine accuracy?

Slay the Spire is a mouse-driven deck-builder.

Crypt of the Necrodancer is a rhythm-based roguelike that uses only four keys to play.

Both are excellent.

Might I recommend the timeless classic Heroes of Might and Magic III? Most of the campaigns are not too difficult after you get the hang of things, if I remember correctly. And you can get a hundred hours out of it even if you only play the official campaigns.

Steins;Gate and then Steins;Gate0

You can play Earthbound on an emulator with one hand pretty easily. (bSNES is pretty good)

Rimworld

No end of things to do to I mean with colonists

I recently enjoyed playing yet another zombie survivors and it was a blast, cheap and at least a weeks worth of grinding to unlock all the goodies. Also you only need the WASD keys so you should be set with your broken arm.

Xcom: enemy within and xcom 2. FTL: Faster Than Light.

First thing that came to mind was FTL: Faster Than Light. I used to play on a laptop with no mouse and a lousy touchpad, so I became familiar with the hot-keys.

You can pause the game at any point to stage your attack / defense. Most commands have hot-keys you can press, rather than point and clicking. You might need to use the mouse for a few parts, but given the ability to always pause the game (I think it’s game mechanic really) you shouldn’t have too much trouble since you’re under little pressure to do so quickly.

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

Total War. The campaign is turn based; although battles are real-time, you can auto-resolve them instead, which will remove any real-time elements from the game.