Games

Just FYI, there are a number of controllers out there for people who only have the use of one hand that are relatively cheap. I don't always have the use of both hands, and I can definitely say that it's possible to learn to use regular controllers effectively one handed as well. Both the Logitech F710 and the 8Bitdo Pro 2 work really well in my opinion. People have laughed at me, but the 8bitdo Zero 2 surprisingly works really well too, but is much more limited for inputs and thus, more suited to retro games.

I don't understand. You have two friends, each with a good arm, that's two good arms. Tape your friends together and have them coordinate and BAM: two-handed gaming.

XCom and XCom 2 can be played entirely with the mouse. Minor typing if you want to name your soldiers, but nothing requires quick reflexes. Everything is turn based.

There's an older breakout style game on steam called Shatter that can be played entirely with the mouse and has a banger soundtrack and neat visual style.

Emulation opens up a lot of options for old school turn based games. RPGs, turn based strategy. Any of the Pokemon games gen 1-3 can be played one handed with some clever button mapping. Any game made to use just the Wii-mote as a pointer would also work, but I don't know those off the top of my head.

You might want to look into one handed controllers, or something like the FLIR USB dongle that you can use to map IR TV remote signals to keyboard button presses. Just need to use a remote that doesn't already control something.