On machines where I have to use windows I run start10 to replace the start menu with something a little more bearable. I imagine there's a FOSS equivalent but I bought a license years and years ago so I've never bothered to search.
Unfortunately very high, especially with modern systems using "trusted platform module" (TPM) hardware that can tell the software exactly what's running, at a higher privilege level than the OS
The problem is that modern DRM/anti-cheat often works at the kernel level, or by scanning the entire filesystem and running processes. They don't work on linux by design, so the main route to compatibility is showing that there are enough people gaming on linux that they should seek other options for DRM and anti-cheat
I think the issue of gaming on linux hasn't been performance for a while now (native and wine/proton performance can often beat windows) but compatibility - some games still can't run on linux due to DRM, anti-cheat, etc. Things are gradually improving but I think that's the main barrier for the time being
What I'd really love is a script/shader/plugin that lets me do this within the engine - separate out the sprite and its texture so I can swap them out on the fly. Shouldn't be too painful to implement but it's not something I've seen anywhere before
Tailscale could also work, if they're looking for something with a little less setup difficulty. I haven't used it myself as I'm happy to tinker with WireGuard, but it's supposed to be quite easy to get going and I think the free tier isn't too restrictive.