A little background. I am reviving this old thread as the situation seems to fit my use case, but feel free to move it to it’s own topic.
I have a Canon PIXMA TS3151 wireless printer which @ricklinux and @pudge helped me get working on Plasma.
But these days I have the shiny new Gnome 42 and now I want to install the same printer.
Once I created the groups lp and lpadmin and cups and added myself, I enabled/started the services.
systemctl -a list-units | grep -i cups
and they are up and running.
and I modified the /etc/nsswitch.conf according to an article by @joekamprad
and installed avahi.
Installed the cups-bjnp and added the printer in CUPS interface.
Not sure if it’s important, but there is an iMac on the network running CUPS (they created CUPS of course 
but our one is a fork of it) so it correctly identifies the printer as being on @iMac. I’m wondering since the CUPS server is running on iMac, this could be a network problem, as it printed before on the same home network. The print spooler on the mac is empty.
Here are the CUPS pages.
then it times out without printing.
Here is the printer installed in Gnome
I have disabled firewalld for the time, just to be sure.
Here the portscan does not detect the Canon printer.
What am I missing here?