Mac – How to set up Time Machine to back up to a specific folder in the Synology NAS

No, you cannot. Backing up to a local volume (what you're having the server do) uses a slightly different backup format than a network backup (what your server is allowing clients to do). With a local volume backup, the backups are stored inside a folder named Backups.backupdb which is at the root of the backup volume (not in a subfolder). With a network backup, the backup is stored inside a disk image, and the Backups.backupdb folder is at the root of the volume inside that. Because the network backup is wrapped in a disk image, that image can be almost anywhere (volume root, folder, subfolder, whatever); but this flexibility does not exist for a local volume backup.

add the nas hostname and IP to the MAC "hosts" file, that's how fixed it today.

to edit the host file on a MAC, best way is through terminal, google it.

Good luck