Samba AD domain: Provisioning of a Windows 2016 DC:
Actually a Windows 2016 DC can't join a Samba AD domain with a Samba AD DC which is also the SchemaMasterRole owner because the Windows 2016 DC needs the Windows management instrumentation (WMI) protocol for several tasks. Unfortunately Samba doesn't support WMI.
To work around the problem, you require a Windows Server 2008 DC in the domain which is also the SchemaMasterRole owner to join the first 2016 DC.