In case someone ran into the same problem here is how I solved it.
I had a feeling this was http mounts issue. I checked and looks like during update process the .xo-server.toml got deleted. I copied the sample one from the /opt/xen-orchestra/packages/xo-server/sample.config.toml , edited the http.mount and bob's your uncle.
I have a feeling this has something to do with the format of that file change. When I originally built from source the file has a slightly different syntax and it was called .xo-server.yaml. At least according tot he directions I used to build. In any case its all back to normal now.
Thanks you everyone for your help.
that's relatively easy to explain, only the naming is doubled:
the backup-hdd are local disks raid1 in xcp-ng and there brought to xcp-ng as a local "vmbackup" volume, called vmbackup
on xcp-ng-volume a disk is created with the name "backup_raid1_1tb" and connected as 2nd disk (xvdb) to XO
to make the disk available for backup-usage the disk xvdb is mounted via "remote" as a local
now usage for backup-ng is possible, but the usage is not xo_disks
I've replied on github. For sure the VMs should not boot. Of course the source vm has autopower on parameter becouse it's needed.
The problem is big: DR copy of Second Active Directory server is up.... for sure I can expect AD problems in a while...
Autopower on is set up: