here are the steps needed to get Hardware Acceleration in at least a linux vm, https://forum.proxmox.com/threads/virgl-hardware-accelerated-h264-h265.137023/
this gives hardware accleration for things like h264/h265, vc1, vp9, so on.
I just started the make deb portion, it's failing when it gets to the
FAILED: libcommon.a.p/hw_display_virtio-gpu-virgl.c.o . Applied the patch from pve-qemu/qemu directory with patch < virgl.patch
##edit
I started the process on another...