They kinda do…
https://support.plex.tv/articles/201553286-scheduled-tasks/
(Unsure if this is a PlexPass thing only though?)
Above will make a backup of the database
If you want to backup all your metadata, then I suggest a scheduled rsync task in QTS backup station
You’ll need to backup the complete Library directory, that you can find in the QNAP FAQ in Q11, in a library below that named Library
