OK, the Snaps need the CUPS Snap to actually be able to print, so you
need to re-install it:
sudo snap install cups
I asked you to remove it to have better control on the recovery of the
system's CUPS, but now as we have re-established its original
configuration you can re-install the Snap.
Snap, as immutable and encapsulated packaging format gives a higher
security against malicious actions from applications, which allows to
install applications which are not packaged by the maintainers of Ubuntu
or persons especially trusted by them. This way we get a wider range of
easily installable applications, similar to apps in the app stores for
smartphones.
These encapsulated applications have to communicate with your system, to
access the network, the resources of the desktop, ... and also the
printing system. This is done by well-defined interfaces, to let them
only access what they need.
For printing Snaps must access CUPS, but CUPS does not only accept
inquiries for listing the available printers and doing print jobs, but
also for administrative tasks, like creating and modifying print queues,
and even reading or deleting jobs from other users. Newer CUPS versions
have a so-called Snap mediation, a mechanism that sees whether inquiries
come from a Snap and whether they are permitted to send administrative
tasks and reject them if not. As not every CUPS version has this
facility, we run the inquiries through the CUPS daemon of the Snap,
which always has this functionality. The CUPS Snap installed on a system
which already has a classic CUPS runs in the so-called proxy mode and so
it only passes through the non-administrative inquiries to the system's
CUPS.
You only need to have the CUPS Snap installed, you do not need to
configure something on the snapped CUPS, it sees your print queues
automatically and passes them on to the application Snaps.
If applications still do not print, perhaps their printing interface is
not connected. You should manually connect the interfaces then. Note
that some need the "cups" and some the "cups-control" interface.
So run
snap connections | grep :cups
If all is correct you should see lines like the following in the output:
cups-control firefox:cups-control :cups-control -
cups-control thunderbird:cups-control :cups-control -
If not, you need to run
sudo snap connect firefox:cups-control
and/or
sudo snap connect thunderbird:cups-control
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You received this bug notification because you are a member of Ubuntu
Desktop Bugs, which is subscribed to gnome-control-center in Ubuntu.
https://bugs.launchpad.net/bugs/2083530
Title:
gnome-control-center not able to add printer or make settings
To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/cups/+bug/2083530/+subscriptions
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