I have the same problem for my hades canyon nuc8i7hvk.
I followed the PCI Passtrough wiki, both Intel Virtualization and VT-d are enabled.
Tested multiples guest OS (kernel >= 4.18 support for AMD VEGA), the VM starts but as soon as I get output over HDMI every thing hangs including the Dom0.
After a hard reset, nothing related to passtrough in theses log files: SMlog, xensource.log and hypervisor.log.
The problem is explained in the Intel documentation (Link below page 63): "lack of Access Control Service (ACS)"
https://www.intel.com/content/dam/www/public/us/en/documents/specification-updates/xeon-e3-1200v3-spec-update.pdf
There is a success story using Fedora and ACS patched kernel to change IOMMU groups.
Please is there a way to disable the kernel ACS check for XCP-ng ?