CUPS is run by root
To administer a single service remotely using root is not a good idea specially when you have to delegate limited access to someone else.
Additionally root login is disabled on ubuntu.
I cups the workaround is to allow a group or groups to do the administration. The default group is lpadmin i.e.
One can change it or add another group to it but the better way is to add the user to this group who will be responsible for cups administration.
# Administrator user group...
I don't know about the server versions but on desktop version the default first user is also a member of lpadmin group. On server version i guess the user scheme is different and there is no user present for this purpose therefore a user needs to be created who will be a member of lpadmin group and can do the cups administration.
The cupsys user is obsolete I guess because everywhere in the documentation root is mentioned now and this is the user under which cups is running.
These are my findings so far.
Just tested the cups and remote administration by creating a new dummy user who is a member of lpadmin group only and it successfully logged in did administration tasks like adding and deleting printer, setting deafults for the printer, sharing over network etc. So now I can confirm the a user needs to be only the member of lpadmin group to handle cups administration.