Fresh UCS 5 install, missing SRV records

I have just done a fresh UCS 5 install and created a new domain. My Windows PCs cannot join the domain. I get an error indicating that there is no _ldap._tcp.dc._msdcs.[domain] record. When I view DNS records in the web interface or query with nslookup, indeed there is no such record.

I can’t find similar instructions to those posted for UCS 4 here, which are not appropriate for UCS 5. I’m not even sure if samba is running. I get nothing when I type systemctl -a | grep samba.

Please, can someone help me this time? The reason I have resorted to installing fresh and creating a new domain is because no one responded for my requests for help to fix my original installation.