@andriy.sultanov It's possible that this is just a fundamental issue with trying to use (maybe just Battlemage) Intel GPU's in XCP-ng.
The card itself appears to be a PCIe bridge in front of the actual GPU hardware on the card. If the driver on the guest requires "the whole thing" sent to it, and you can't pass-through the whole bridge and everything behind it, then there's no real way to use these GPU's in a guest on XCP-ng.
The lack of recent kernel or sufficient backports in the XCP-ng kernel, means the SRIOV features of Intel GPU's are lost as well.
All of this stuff works in Proxmox with seemingly little issues.
James