This issue can be worked around for now by manually setting the VKD3D_VULKAN_DEVICE environment variable (for me it's 1).
I think this confirms that it is a vkd3d-proton issue and not a driver issue.
I can work on a fix myself in a few weeks if no one gets to it before then.
I am on a laptop that has both integrated graphics on the Intel CPU and a discrete NVIDIA GPU. When games are launched on Proton, they should be selecting the dGPU to run on, but when on D3D12 they consistently only use the integrated graphics.
__NV_PRIME_RENDER_OFFLOADdoes not solve the issue, unfortunately. The discrete GPU still shows up at 0% usage in my system monitor and the game will run at less than 10 FPS.This only occurs with D3D12 - when I run a game that uses Vulkan or D3D11, the NVIDIA GPU gets picked, as expected.
Software information
I have tested this with Satisfactory (D3D12 vs. Vulkan rendering backends), Deep Rock Galactic (D3D12 vs. D3D11 rendering backends, and Forza Horizon 5 (only D3D12 and just won't run).
System information
Log files
steam-548430.log