I clicked randomly on a number of motherboards sold by the 2 brands that came to my mind, Asrock and Gigabyte, and all of them advertised hdmi and usb-c graphics output so I am surprised by your declaration that consumer motherboards don't have GPU. If I am not mistaken on AMD Ryzen architecture it comes down to choosing a CPU with a G or 3D suffix which states they have an integrated GPU.
It really still is the case that most if not all consumer motherboards don’t have built in graphics. For the most part especially on the intel side, they’ve relied on the iGPU in the CPU for output for probably 10 years now
Well my case still stand that you still have an integrated graphics, if not by the motherboard but the GPU, that you can use on the host while you dedicate a discrete card for VM passthrough.
Desktop Ryzen 4's and newer have a very small iGPU that's just enough to put up a desktop (and presumably a framebuffer fast enough to feed a discrete card's output into)
