Hi to all,
comparing avahi settings was much less pain then I expected.
On the installation with ipp-usb not working the file
had an active (non commented out) line:
On my installation with ipp-usb working this line in the respective
So it is commented out and names a different interface.
After commenting out this line in the problematic installation the
printer is visible and configurable in the cups administration. As with
the other installations, two printers show up in the print menue
(Libreoffice) and I can print successfully.
I have no idea how this setting ended up in /etc/avahi/avahi-daemon.conf
Thanks to all who helped finding the flaw. Feel free to contact me if
you think I could help here in the region where I live (Aachen/Germany).