You may try with CIFS external storage management (login through NextCloud with username/password will be used for access to SAMBA).
You should enable the Apps:
Then in Admin panel, you should go to External Storages:
I've tried on NS 6.8 and it works pretty well and seamless, not sure if it works with NS7 + SAMBA AD.
I would ask @giacomo to elaborate his answer, because if this is the case I may also overlooked the security point of view.