Realm join command fails with the Error "realm no such realm found"

Issue

• Realm join command fails with below error.

realm no such realm found

• realm discover command failed with the below error.

See: journalctl REALMD_OPERATION=r6604.6960
realm: No default realm discovered

• Journalctl revealed the following error messages concerning Active Directory domain ad.example.com.

sl.example.com realmd[6993]: Using 'r6940.6990' operation for method 'Discover' invocation on 'org.freedesktop.realmd.Provider' interface
sl.example.com realmd[6993]: Registered cancellable for operation 'r6940.6990'
sl.example.com realmd[6993]:  * Resolving: _ldap._tcp.ad.example.com
sl.example.com realmd[6993]:  * Resolving: _ldap._tcp.ad.example.com
sl.example.comrealmd[6993]: Resolving ad.example.com failed: No DNS record of the requested type for '_kerberos._udp.ad.example.com'
sl.example.com realmd[6993]: No DNS record of the requested type for '_ldap._tcp.ad.example.com'