x11-libs/libva-intel-driver does not support Tiger Lake, and probably other new Intel GPUs, per https://github.com/intel/intel-vaapi-driver/issues/531
x11-libs/libva-intel-media-driver should be used instead
But there is no keyword to instruct libva-2.11.0.ebuild to depend on libva-intel-media-driver
There is iris VIDEO_CARDS keyword, I'm not sure if it should be used to make libva depend on media-driver, or there should be a new keyword.
But either way libva should be able to switch between intel and media drivers based on a keyword
CCing Evgeny in case he has input (add yourself to the packages!)