For the tests we had a need for 1 week ago, it's now fine, however I'll probably update this thread once we have an ISO image that can be tested by users that have such hardware. Note: it's not about using the GPU itself, but simply about making sure that the hypervisor works well with the changes we made to replace the not-built-by-us gpumon tool whose absence would make XCP-ng 8.1 unbootable (as we sadly found out after the release) with a dummy one built by us.
Now is time for the tests I was talking about earlier. XCP-ng 8.2 beta is now available with our dummy gpumon and we need users who have nVIDIA GPUs to test it and give us feedback. There may be situations we have not tested where our dummy gpumon is not enough to make the XAPI happy, despite the fact that we don't support nVIDIA vGPUs (proprietary software from Citrix required for that feature).