Debian 10 backports repository is broken
This one (https://build.opensuse.org/project/show/Debian:10)
It uses backports only for amd64 not for others eg i386

x86_64 http://ftp.de.debian.org/debian/buster-backports/main (deb)
s390x http://ftp.de.debian.org/debian/buster/main (deb)
ppc64le http://ftp.de.debian.org/debian/buster/main (deb)
aarch64 http://ftp.de.debian.org/debian/buster/main (deb)
armv7l http://ftp.de.debian.org/debian/buster/main (deb)
i586 http://ftp.de.debian.org/debian/buster/main (deb)

should be
x86_64 http://ftp.de.debian.org/debian/buster-backports/main (deb)
s390x http://ftp.de.debian.org/debian/buster-backports/main (deb)
ppc64le http://ftp.de.debian.org/debian/buster-backports/main (deb)
aarch64 http://ftp.de.debian.org/debian/buster-backports/main (deb)
armv7l http://ftp.de.debian.org/debian/buster-backports/main (deb)
i586 http://ftp.de.debian.org/debian/buster-backports/main (deb)