Steps I have done to make NVIDIA vGPU works:

1. Install XCP-ng 8.2.1
2. Install all update yum update
3. reboot
4. Download NVIDIA vGPU drivers for XenServer 8.2 from NVIDIA site. Version NVIDIA-GRID-CitrixHypervisor-8.2-510.108.03-513.91
5. Unzip and install rpm from Host-Drivers
6. reboot again
7. Download free CitrixHypervisor-8.2.0-install-cd.iso from Citrix site
8. Open CitrixHypervisor-8.2.0-install-cd.iso with 7-zip, then unzip vgpu binary file from Packages->vgpu....rpm->vgpu....cpio->.->usr->lib64->xen->bin
9. Upload vgpu to XCP-ng host to /usr/lib64/xen/bin and made it executable chmod +x /usr/lib64/xen/bin/vgpu
10. Deployed VM with vGPU and it started without any problems

So I did not make any modifications with emu-manager.

My test server is far away from me and it will take some time to download the windows ISO to this test location. Then I will check how it works in the guest OS and report back here.

@wyatt-made I need few days to test it.
Will report later here

Finally after a week I found the solution!
There is no problem with emu-manager.
XCP does not contain necessary package vgpu.
I copied vgpu from Citrix ISO and now it is alive! : )

xe vif-unplug uuid=[vif_uuid]

or use XenCenter and on Network tab press button Deactivate

Maybe this idea will help

xe vm-list params=networks | awk '{print $5}'| sed 's/.$//'

This problem is due to the fact that I was connecting to the VM through the console. After connecting via RDP, everything began to work correctly.

Hello!

I have test server with AMD Epyc 7282 and AMD FirePro S7150x2.
I installed host drivers revision 2.0 and guest drivers revision 20.Q2.2 from official AMD site
As guest I'm using Win 2019 Standard edition.

Everything runs ok excepting that for some reason MxGPU does not support OpenGL at all....

Tried reinstalling VMs OS, drivers, etc. Nothing helped.

The description of the driver says that it must support OpenGL 4.6
I have software that requires OpenGL 2.0+, so without OpenGL it will not even start.

Does anyone have any successful experience with MxGPU and OpenGL 2.0+?

You can get it with such command

xentop  --vcpus -i 2 -b | grep -i "Domain-0"

Skip first line because it always return 0.

Or you can use method that using XO.
Get host_rrd data from host and parse it
https://xapi-project.github.io/xen-api/metrics.html

I do not have now host with GPU to test, but maybe you can try on/off this option in VM BIOS.

Console options -> Console Output Device Select ->

And another option is to add video=efifb:off to the grub config

Did you try this tool?
https://parsec.app/

@Huursa open source doesn't equal free. You must read the Citrix license for 7.3 Xenserver. If it allows the use of packages, then no problem. But as far as I know (remember), the license for the free version of Xenserver does not allow commercial use.

Hello!

You can check my investigations of this question here

Haha, it finally works!!!

The problem was with the template I used to deploy the VM.
I first deployed a VM from the default Windows 2019 template and it was not possible to install the GPU drivers.

After that I tried deploying the VM from the "other installation media" template and now I can install any drivers.
To make it work with different benchmarks, I installed the Quadro RTX 5000 driver (from consumer site).
The result is on the screen. About 60 average FPS.
I think it is limited with driver on host.
As you can see FurMark detected GPU correctly T4-Q8.

Result from eth classic miner.
Miner detected GPU as T4 too.

No licenses are required : )