HP printer unavailable with firewalled.
 

I have installed firewalld on my Debian 12 install and opened up ports 631 and 9100 on both tcp and udp, like I do when running Fedora, for my HP printer. The printer is a driverless HP Color LaserJet Pro M453. I have not changed any settings on the printer, for a very long time. Yet the system can't find the printer either for setup or printing. I have confirmed that the problem is firewalld, by running:
Then I was able to configure the printer. Now that I have firewalld back on, I can't print to the printer, and I get a "no suitable host found" error.

Is there something that Debian 12 does differently with firewalld, or the ports that printers connect to the system on?

It depends on how strict are your firewall settings. Are you using IPP everywhere printing? Do you have a URL like
ipps://HPA8B13BBAA8DA.local:631/ipp/print

You might need to open mDNS port 5353 UDP. cups uses cups-browsed and/or avahi to automatically find printers which uses mDNS.

Thanks for the reply. The connection is listed as "implicitclass://HP_Color_LaserJet_Pro_M453_4_E70F39/". The listing is the same in KDE printers section, as well as when I go into CUPS http://localhost:631/printers/