I just want to add that I am seeing the same issue with Ubuntu 24.04.3. Creating a VM does work, but it crashes immediately when trying to start it for setup.
I have not yet tried the approach of starting with 24.04(.00) and then upgrading to the lastest version due to lack of time.
We are still using XCP-NG 8.2.1 on the server in question. If an upgrade to 8.3 solves the issue, please let us know. Reading the thread, it appears to have the same problem, though.
Processor is an AMD Ryzen 9 3900X. We have not had any other issues with the system and it's been running for a few years.