I know less than nothing about all of this, I’m just transporting collected info I heard and saw, stashed in my memory. In general, the nvidia driver is very X-centric with sometimes weird behaviour, changing on whether an Xserver is running or not:
https://forums.developer.nvidia.com/t/nvidia-smi-no-device-where-found/197768/19?u=generix
vkcube running on an nvidia egpu displaying on an Xserver only running on the amd gpu.