I can't get the igpu to output anything too. It only works with ubuntu. What I noticed: With IGPU Passthrough you won't see the bios/uefi screen in windows / ubuntu booting. The Display will only show something, when ubuntu loads (probably loading the driver or it resets something on boot up? idk maybe someone know how the gpu is initialized under ubuntu). When I passthrough a dedicated gpu (Nvidia 3060ti) it will also show the bios/uefi screen (and works in windows).
So I guess it has something to do with seabios / OVMF or maybe also q35 / i440fx not initializing the igpu correctly.
So I guess it has something to do with seabios / OVMF or maybe also q35 / i440fx not initializing the igpu correctly.