How to disable (PCI unmap?) an iGPU?

[T-X]

I'm running into strange issues with SteamVR overlays. And the tickets I found so far all seemed to have in common that people were having multiple GPUs. So it would be very insightful if I could disable the iGPU completely.

Is there a way to disable an AMD/ATI based iGPU? Unfortunately I also have an AMD/ATI eGPU, so I can't just blacklist the amdgpu kernel module. Also running echo "0000:33:00.0" | sudo tee /sys/bus/pci/drivers/amdgpu/unbind does not seem to work, that seems to leave the iGPU enabled and instead creates kernel splats in dmesg. Thirdly, what I read online was adding vfio-pci.ids=1002:1681 to the kernel arguments in Grub. vfio-pci confirms adding 1002:1681, the ATI/AMD Radeon 680M iGPU, in dmesg. But the iGPU + laptop screen still is used and unbinding still won't work. Another issue is that I can't power on the laptop with the Razer Core X Chroma eGPU enclosure connected, as then the Lenovo Thinkpad T14s will just complain about not enough power and will refuse to continue booting. So during the Grub menu is currently the earliest I can connect the eGPU, I think.

Any other ideas regarding how I might be able to disable the iGPU?

https://gitlab.freedesktop.org/monado/monado/-/issues/267
ValveSoftware/SteamVR-for-Linux#496
ValveSoftware/SteamVR-for-Linux#202