Hi @fasttech, thank you for testing the restore procedure again!
It is important to know the exact date of the backup, because we fixed a bug (do you remember 5188?) during rc4. See this comment on Jan, 13th:
The Samba secrets.tdb backup action was moved from nethserver-samba to nethserver-sssd. Old backups could not include secrets.tdb. In that case, automatic config restore is incomplete and a manual re-join to DC is required. See this procedure.