Here's the config file I am using:
$ cat /usr/share/pam-configs/sss-gss
Name: Authenticate if the user can obtain a valid Kerberos ticket for the local host
Default: yes
Priority: 512
Auth-Type: Primary
Auth:
[success=end default=ignore] pam_sss_gss.so
Auth-Initial:
[success=end default=ignore] pam_sss_gss.so
However it can't be added to the package yet because it will break
authentication for non-local users (beacuse we use the 'use_first_pass'
option with pam_sss.so when it's not the initial module, so a non-local
user is not able to log in when pam_sss.so is not the initial module and
no prior modules stashed a password for it to consume).
For the time being we need 'use_first_pass' so that non-local users
don't get prompted by _both_ pam.unix.so and pam_sss.so.
Ideally pam_sss.so would have a 'try_first_pass' option which would
unblock us from shipping an sss-gss pam config. I've filed an RFE here:
<https://github.com/SSSD/sssd/issues/6946>.