Fresh install of OMV 3.x and openmediavault-plexmediaserver plugin.
Data disk contains plexmediaserver database from OMV 2.x installation.
After installing the openmediavault-plexmediaserver plugin and pointing the Database Volume to the previous install location, Plex continues to use /var/lib/plexmediaserver (verified with lsof).
Fresh install of OMV 3.x and openmediavault-plexmediaserver plugin. Data disk contains plexmediaserver database from OMV 2.x installation.
After installing the openmediavault-plexmediaserver plugin and pointing the Database Volume to the previous install location, Plex continues to use /var/lib/plexmediaserver (verified with lsof).
The home directory is unchanged:
Manually changing the home directory solves the problem.