Comment 1 for bug 1477106

Since the bug report is very old, the original cause for what is described here may have changed. But on a focal system, the gtk print dialog populates the printer list on its own. Even if cups is not running locally, it queries avahi-daemon and produces a list of printers. This is causing a number of issues, including printer duplicates, printer entries that don't work, printers that are labeled in a weird way etc. It is silly that such broken behaviour cannot be turned off. In any case, until this improves, users may choose to use a patched version of gtk3 where the broken avahi lookup is removed from the printer dialog:

https://launchpad.net/~launchpad-weyland/+archive/ubuntu/libgtk3-no-avahi/

Also see lp:1379359 and lp:1753509