Canon imageRunner advance C2020 not working with CUPS on PureOS

Question

Librem computer using PureOS v9.0 (amber).

I can connect the computer to the Internet using the Wifi card, so the Wifi is working. Uncomplicated Firewall (ufw) is disabled.

If I connect the computer directly to the printer using a USB cable, it auto-detects the printer (using SNMPv1 I think) and install it in CUPS. It uses the Canon iR-ADV C2020/2030 Foomatic/Postscript driver. However, even on USB, the printing does not work: CUPS think it managed to successfully send the printjob, but the printer flashes an error and does nothing.

But trying to setup the printer through Wifi (using a network printer at http://192.168.0.15:9100) only shows "The printer is not responding" in CUPS, so it can't even connect to the printer. The CUPS error log does not provide more details.

Pinging 192.168.0.15 fails, and trying to navigate to http://192.168.9.15/ also fails (although it might be because the printer does not have a webpage to serve).

Any idea what I should look for next? Thanks!