gtk4 has more failing build tests than other architectures. Unfortunately, we are forced to ignore them because our understanding is that it's currently required for desktop tasks to be installable on all release architectures. (Or I guess someone could fix the bugs but that can be difficult.)
If you have screenshots to demonstrate s390x breakage that may be gtk4's fault, please forward them to the Debian bugtracker for gtk4. Thank you, Jeremy Bícha
