Run omv-confdbadm migrate conf 5.2.0 from CLI.
Should have run during some of the updates.
Did you update to the latest version?
After following your advice, I was able to uninstall the plugin. All updates completed successfully. I was able to install the nut plugin successfully, configure it in the UPS section, and apply the configuration without any snags.
Thank you very much for your time and help!