Request for testing: GTK for bullseye with improved CUPS printing support

I have been looking into two GTK merge requests [!6] and [!9], trying to
figure out which one is the better candidate for a bullseye stable update.

[!6]: https://salsa.debian.org/gnome-team/gtk3/-/merge_requests/6
[!9]: https://salsa.debian.org/gnome-team/gtk3/-/merge_requests/9

This is an attempt to resolve https://bugs.debian.org/982925, and maybe
other printing-related issues. Not all GTK programs necessarily use the
unmodified GTK printing dialog, but the gedit package seems to be a good
test-case.

At the moment, I am leaning towards the more complete !6 being a better
candidate for a stable update, even though it is technically a feature
enhancement, which we don't usually do in stable. Please could people who
have printers try the release candidate from here, and confirm whether it
works as expected?
    https://people.debian.org/~smcv/bullseye-gtk-printing/mr6/
    https://salsa.debian.org/gnome-team/gtk3/-/commits/wip/bullseye-mr6

The _binary.changes and .dsc files are signed with my key in the Debian
keyring, and can be verified with the dscverify tool from the devscripts
package (this requires devscripts and debian-archive-keyring installed).

If the release team will not accept !6, then the fallback option is !9:
    https://people.debian.org/~smcv/bullseye-gtk-printing/mr9/
    https://salsa.debian.org/gnome-team/gtk3/-/commits/wip/bullseye-mr9

Please send test results to #982925. There are a lot of moving parts here,
so when reporting test results, please answer these questions:

* Which versions of cups-daemon and cups-filters-core-drivers are installed?
* What printers are physically present on your network?
* Have you configured a printer queue in CUPS manually, or are you relying
  on auto-detection?
* Is cups-browsed installed? If yes, which version?
* What printer names appear in the GTK print dialog?
  (If they contain MAC addresses or serial numbers, you can censor them
  as XXXXXX)
* For each printer name that appears:
  * Does it appear in /etc/cups/printers.conf?
  * Does printing to it work?
  * If not, what failure mode do you see?
    (Nothing happens / printer prints wrong results / other)

Please note that I do not claim to be any sort of expert on printing.
Anyone who thinks they can do a better job is welcome to take over
any time.

Thanks,
    smcv