KDE/Plasma: Adding a printer doesn't work

[Terry Barnaby]

In Fedora29 it doesn't seem possible to add a printer as a normal user 
from the "System Settings" application. When you try there is an error 
message in the "Add a New Printer" dialog "Failed to get a list of 
devices: 'Forbidden'".

On Fedora27 and before this worked fine (you did have to enter the root 
password multiple times, which was a big pain, but at least it worked).

Any ideas if this should work properly ?

Terry