Modern GNOME based distros automatically discover and install printers on your network and there’s no easy way to disable this. In the past disabling cups-browsed was enough, but we also now need to disable Avahi discovery (Avahi is a zero-configuration discovery client).
Firstly edit the avahi-daemon.conf file to essentially disable networking for the service. Disabling the service with systemd results in a long delay when opening a printing dialog, so disabling networking is a clever way to essentially disable Avahi without any negative effects.
sudo nano /etc/avahi/avahi-daemon.conf
... use-ipv4=yes use-ipv6=yes ...
... use-ipv4=no use-ipv6=no ...
Then restart the avahi-daemon service:
sudo systemctl restart avahi-daemon
Lastly, you’ll still need to disable printer discovery in cups-browsed.conf too as we did in the past. You can do this with:
sudo nano /etc/cups/cups-browsed.conf
Find the BrowseProtocols line (ctrl+w will bring up search in Nano), and then uncomment the line (remove the
# at the beginning of it) and save the changes.
Then disable cups-browsed:
sudo systemctl disable cups-browsed sudo systemctl stop cups-browsed