[cups] Printing via SMB-Kerberos not working in Ubuntu 18.04

[Alex Persson]

After upgrading from Ubuntu 16.04 to 18.04 printing via SMB-Kerberos no longer works.

In 16.04 I can just type "lpr file.pdf", but when doing this in 18.04 I get "Password for [myuser] on localhost?" and it expects me to type my password instead of using my Kerberos ticket for sending the print job to the print queue.

I have "AuthInfoRequired negotiate" in /etc/cups/printers.conf
The file /usr/lib/cups/backend/smb is a symbolic link pointing to /usr/lib/x86_64-linux-gnu/samba/smbspool_krb5_wrapper (in 16.04 it was pointing at /usr/bin/smbspool_krb5_wrapper).
The permission is 700 on /usr/lib/x86_64-linux-gnu/samba/smbspool_krb5_wrapper.
The version of cups is 2.2.7-1ubuntu2.1 in 18.04 while it was 2.1.3-4ubuntu0.5 in 16.04.
The version of smbclient is 2:4.7.6+dfsg~ubuntu-0ubuntu2.2 in 18.04 while it was 2:4.3.11+dfsg-0ubuntu0.16.04.16 16.04.

Can anybody please help me figure out what the problem is?

Best regards, Alex