@till.kamppeter - this thread is getting fairly unwieldy. The discussion about authentication is different than what this topic is about. Can you create a new topic for ‘user authentication in snapd’ describing how and why CUPS is authenticating users on the system as opposed to maintaining its own authentication db (ala htpasswd). Feel free to copy/paste my comments from Snapping CUPS Printing Stack: Avahi support, system users/groups. When that is done, we can involve others more easily.