Wine/Proton (Codeweavers and independent contractors). Proton is open source even if it’s mostly Steam specific.
Mesa RADV (Vulkan AMD driver)
The Linux kernel
KDE Plasma
gamescope
HDR/colour management
That’s just off the top of my head. I’ll admit that some of this work comes from 1 or 2 single paid developers that have their hands in many things, but that’s not a bad thing.