I'd actually _like_ to use Xen, but as far as I can see is just dead in all but name.

To name one example, nested virtualization support is not only hopelessly broken, it's MORE broken in recent releases than it was a decade ago. You can see right here how the feature kept getting broken by every other release until nothing worked anymore: https://wiki.xenproject.org/wiki/Nested_Virtualization_in_Xe....

And Xen is literally the only virtualizer out there that does not support nested virtualization, which is a rather critical feature since many (dev) stacks assume one has hardware virtualization, and Windows is going to require it sooner than later.