Linux

All GPUs released since they came out with the RTX 2000+ line are supported and all new GPUs will most likely have support, especially with this announcement saying they're committed to it. There's a support list on their GitHub and it includes all the weird little things you'd be worried about. Even silly little laptop chips like the new RTX 500 are on it.

I think the only reason they limited GPU support is because the older ones physically don't have the hardware for this approach; they switched to their newer RISC-V "GSP" processors with the RTX line. In the new open module, all of their proprietary "secret sauce" was shoved off to firmware running on that new GSP. Previously, their proprietary kernel module loaded all of that same secret sauce as a gigantic obfuscated blob running on your normal CPU instead. The Windows side of their driver has also been moving towards using the GSP, they even advertised it boosts performance or whatever, and I can believe it.

That said, with this new stuff, the official Nvidia userland portions providing Vulkan/OpenGL/CUDA support and the like are still proprietary. It's still worse than AMD in that regard. But at least it's possible to replace those bits, and Mesa/NVK are working on getting Vulkan up and running (with NVK supposedly getting pretty damn good, and Mesa's OpenGL-on-Vulkan is pretty good too so that's free).