Strings from many .ui files are no longer translatable
If you scroll down in https://l10n.gnome.org/POT/gtk.main/gtk.main.pl.po, you’ll notice that many strings are suddenly obsolete in the .po files. This seems to be caused by translatable="yes"
having been replaced by translatable="1"
in many .ui files, and our infrastructure (gettext?) can’t handle that.
18 files are affected. https://gitlab.gnome.org/GNOME/gtk/-/blob/main/gtk/ui/gtkaboutdialog.ui is one example.