Artemis/Apollo are mentioned in the post above - yeah they work better than the out of box experience, but you still have to configure your physical screen to be off for every virtual display. It unfortunately only runs on Windows and my machine usually doesn't. I also only have one dGPU and a Raphael iGPU (which are sensitive to memory overclocks) and I like the Linux gaming experience for the most part, so while I did have a working gaming VM, it wasn't for me (or I'd want another GPU).
> Built-in Virtual Display with HDR support that matches the resolution/framerate config of your client automatically
It includes a virtual screen driver, and it handles all the crap (it can disable your physical screen when streaming and re enable after, it can generate the virtual screen by client to match the client's needs, or do it by game, or ...)
I stream from my main pc to both my laptop and my steamdeck, and each get the screen that matches them without having to do anything more than connect to it with moonlight.