This was the old method for configuring AD for SQL on Linux and used to work for RC4 encryption. We learnt that ktutil has a defect which does not allow correct salting of the entries and this will NOT work for AES encryptions. Since the RC4 is disabled by default in RHEL 8 for security reason, this process will definitely not work on RHEL 8 unless security is relaxed. We revisited the process and rewrote it to use ktpass directly on the AD server or a Windows server to generate the keytab instead.
I would highly encourage revisiting the process mentioned here and change it to conform to the new guidance of using ktpass at following link. It is much cleaner and repeatable, as well as scriptable in most cases.