Here it is how it works for me:

1. In Deja Dup open Storage tab and choose Windows Share from drop-down list.


2. In Server enter ip address of your samba server.


3. In Folder enter path to path to directory where you want to store your backup.


4. In Username enter your samba username.


5. In Domain Name enter domain in which your samba server resides.

The only problem is that Deja Dup wants password every time it makes a backup. I guess solution is to mount samba share using fstab.

Hope it helps.