Starting from a minimal text install, I installed XEN (both "Xen server" and
"Xen tools") via YaST, but the xen-kernel package was not installed. I would
expect that installing "Xen Server" would include the xen-kernel and add the
appropriate Grub boot entry.

In order to install Xen via YaST I had to install the vm-yast2 pacakge, as it's
not included in the minimal install pattern. I would expect it to be part of
the minimal install pattern, as I would think it would be common to install Xen
on an otherwise bare host to use as a Xen dom0/host.

https://forums.opensuse.org/showthread.php/506319-Xen-Installation-Fail