I’ve never had this issue with any distro before, so I don’t know where to begin troubleshooting. Avahi, cups, and plasma’s printer configuration packages are all installed (I just checked “printer support” during installation). When I click “Add printer”, it seems like it looks for a printer on the network, then fails falls back to manually entering IPP addresses/paths.
The printer is on, awake, and connected to the WiFi. What are the first steps I should take for troubleshooting?