As announced in #1148038, new upstream releases of WebKitGTK no longer
support big-endian architectures.

swt4-gtk currently builds an Architecture: any package,
libswt-webkit-gtk-4-jni, which Depends on WebKitGTK libraries. Please
limit building of this package to little-endian architectures, so that
we can remove its old s390x binaries without them coming back (and being
uninstallable) in the next upload.

One way to do this would be something like (untested)

 Package: libswt-webkit-gtk-4-jni
-Architecture: any
+Architecture: amd64 arm64 armhf i386 loong64 ppc64el riscv64
 Depends: libswt-gtk-4-jni (= ${binary:Version}), libwebkit2gtk-4.1-0, ${shlibs:Depends}, ${misc:Depends}

Or the package could be disabled on big-endian architectures by
something like this in debian/rules (again untested)

ifneq ($(DEB_HOST_ARCH_ENDIAN),little)
dh_options += -Nlibswt-webkit-gtk-4-jni
endif

and then passing $(dh_options) to all dh invocations.

This will make two packages (biglybt and davmail) uninstallable on
s390x, but that seems harmless.

    smcv