I had similar problem yesterday when trying to Apply changes after upgrade to the new OMV.
My UPS works well (nutdrv_qx, ID 0665:5161) before and after upgrade, communication still works. But there is an error in journal the nut-driver.service failed.
It because of this service is missing!
The service has different name based on UPS identifier in OMV settings: nut-driver@my-ups.service
And there is a nut-driver.target (after typo "systemctl status nut-" and pressed tab in shell).
At this point you should be able to start/enable
nut-driver-enumerator.servicewhich will automatically create nut-driver@<ups name> systemd service instance and start it.)
So, I searched in omv code and found "nut-driver" in /srv/salt/omv/deploy/nut/default.sls and changed it to "nut-driver@my-ups". And then Apply changes in OMV finally works! But it is temporary solution.