My gaming computer only runs windows currently but since I wouldn’t be able to game when my friends used it I could just reboot into Linux when I’m not using it.

I personally run it on a linux system, but If you wanted to I don’t see why you couldn’t just run docker on your windows install (Make sure you follow the wsl 2 guide, and not the hyper-v one. Docker for Windows doesn’t support gpu passthrough on hyper-v). As for the gpu issue while I’ve never tried gaming simultaneously, I do have several docker containers accessing 1 gpu. So it might be worth a shot to see if they could all, or at least a couple, could play off of the one gpu, but it would depend on how heavy the games you’re playing are of course.

You could set up each of them a Steam-headless docker container. I use one on my nas to game on a very low end laptop.