Comment 9 for bug 1851091

Just attempted OP's advice and downgraded my kernel to 5.0.0.xx and Xen 4.9 boots, albeit with no ethernet support (I assume I need a backported driver, or to install the version of Xen that came with 19.04). So this is definitely a problem with the new Eoan kernel, and it affects the current git tree as I did build my own kernel from Ubuntu's Eoan sources to check and could not boot at all.

Seems like Eoan's Xen support may have rotted out. Sad, would've loved to use Xen instead of attempting to use VMware (considering my processor is now on the VMware unsupported list after ESXi 4.5)