Plex permissions are not working - need help please

[ChuckPa]

If you’re using Linux, why are you using CIFS (SMB)?
That’s totally nonsensical.

NFS is native to Linux (Synology is Linux based)

Install nfs-common on your linux system.
Enable NFS on the Synology

Now follow the tutorial / how-to here

Linux Tips

Mounting NFS network shares for Plex use The basic checklist Prepare the NAS: Create a ‘mount point’ directory structure on your Linux machine which will be where all your media shares are grafted and made available for Plex use. Create an entry in /etc/fstab for each share you wish to mount. Mount and debug as needed A. Prepare the NAS. This is unique to each NAS. In general, you only need grant read permission. Should you desire Read/Write for yourself, we will allow for it On Lin…

You will find a lot of info about these type topics in “Linux Tips”