Hello @Dave Williamson ,
Thank you for responding.
I'm glad that you were able to resolve your issue and thank you for posting your solution so that others experiencing the same thing can easily reference this! Since the Microsoft Q&A community has a policy that "The question author cannot accept their own answer. They can only accept answers by others ", I'll repost your solution in case you'd like to "Accept " the answer.
Issue: Errors with cloud Kerberos trust authentication setup
Error: Set-AzureADKerberosServer : Cannot bind argument to parameter 'Domain' because it is null.
Solution:
Resolved the issue & it was related to MFA. It seems it was important to do these steps in a different order to what was using, may have misread the Microsoft instructions.
follow this video https://www.youtube.com/watch?v=FW3TF0zFWd0 and worked.
If you have any other questions or are still running into more issues, please let me know. Thank you again for your time and patience throughout this issue.
Please remember to "Accept Answer" if any answer/reply helped, so that others in the community facing similar issues can easily find the solution.
Regards,
Goutam Pratti.