OmniOS fails to install on XCP-ng (xen)

[BobTB]

OmniOS guest fails to boot in XCP-ng on version 8.2, 8.3.

Same goes for Illumos and Solaris 11.4.

Installation of OmniOS is fine: create a new vm, set viridian=false and installation progress smoothly.

When booting from freshly installed disk it panics with:
WARNING: Couldn't initialize xpv framework

panic[cpu0]/thread=ffffffffffbca07e0: unable to configure /xpvd nexus

a845404f-702e-41a2-ba19-0cdd1bc6f131-image.png

I've tried several version of OmniOS (and latest OpenIndiana), I also tried Solaris 11.4, tried disabling apix with apix_enable=0 in /etc/system and all without success.
The same setup in xcp-ng 8.0 works.

The interesting thing is that there is an OmniOS image for AMAZON AWS - https://omnios.org/setup/aws which runs on XEN (or did they go to KVM?) so it should actually run? How can I get it to run... it seems very close.

Anyone with an idea of a workaround or even better, a resolution to this.