https://www.reddit.com/r/PleX/comments/k2lj2n/problem_mounting_ntfs_drives_so_they_can_be_seen/
There is a much simpler method to add f.i. a (usb) ntfs (or other) media disk to Plex.
Just plug it in your usb port of the plex server/computer.
The problem is that it will be mounted under /media/<user> (where user is your login)
Linux restricts access to /media/<user> via acls to the <user>
sudo getfacl /media/<user>
The problem is that while adding media to Plex, it cannot "cd" over/to /media/<user>
To fix this, simply add the user "plex" to the acl of /media/<user> wth this command:
sudo setfacl -m u:plex:rx /media/<user>
Optionally you can create a symbolic link to your media folder.
Suppose your media folder is called "films" and it is located on a drive auto-mounted as /media/<user>/mydrive, then you can create a symbolic link at /film:
ln -s /media/<user>/mydrive/films /film
Now you can browse in Plex to that folder /film and view and index your media.