> NVIDIA and AMD can decide to undermine it if Linux doesn't yield enough profits for them.

Can you elaborate what you mean, here? AMD has Mesa drivers for Vulkan 1.2+ compliance; their GPUs will support DXVK and Proton until the hardware breaks, even if they quit today. Nvidia's situation is slightly precarious, but the community has Nouveau and NOVA as hedged bets against them going rogue.

And I can't see why they would ever go rogue - supporting Proton is so easy that many manufacturers do it by accident. Remember, even Apple Silicon supports DXVK on Asahi, despite Apple neither documenting their GPU, writing Vulkan drivers for it or designing their raster hardware around open standards. I'd be shocked if AMD or Nvidia managed to make a card that runs DirectX but refuses OpenGL and Vulkan bytecode in any form.