Most hardware (especially GPUs) is hard to virtualize in a secure manner, which is the entire point of Qubes. People who use it typically buy compatible hardware.
I would expect that most Qubes users (including myself) do not virtualize GPUs and use the CPU to render graphics outside of dom0.
I would expect that most Qubes users (including myself) do not virtualize GPUs and use the CPU to render graphics outside of dom0.