I will try to take a look when I get a chance. You should be able to not make a selection so the database stays in the default location.
Posting here because I'm having similar issues getting Plex running in OMV on my RPI. See here: Plex install trouble
After uninstalling and reinstalling, Plex is now running on the RPI but it will stop running the moment I click "save" on the PMS page where you can Enable PMS. I get a bunch of errors about how the attempts to change ownership failed.
Additionally, the drive that has my music library on it is read-only now, which is exactly the problem I had on my older RPI installation, which I thought might go away with the newer OMV version. It was fine to read/write to before Plex was installed. Kind of defeats the purpose if I can't throw new albums on that drive as I get them.
Any idea what I can do about either of these things?
Thanks!