Kerberos authentication to ADFS

I am struggling with Kerberos authentication to ADFS.

Of course the instructions are for Windowze. I am doing this on a Mac, and eventually need to run it from a Linux machine.

I skipped step 1 - is there a non-Win equivalent?

The rest of the steps were easy to port.

I have to provide my credentials in step 3 when I create the ticket-granting ticket. How come I have to provide my credentials again in step 4?

In the end, I get no errors, only a username : password prompt screen from our AD.

Any ideas?