https://ubuntu-archive-team.ubuntu.com/component-mismatches-proposed.html currently contains the following:
Binary only movements to universe (foundations-bugs)
libc6-dev-amd64-cross libc6-dev-i386-cross cross-toolchain-base
fwupd-riscv64-signed-template fwupd-efi
gcc-13-i686-linux-gnu-base gcc-13-x86-64-linux-gnu-base libgcc-13-dev-amd64-cross libgcc-13-dev-i386-cross libgfortran-13-dev-arm64-cross libgfortran-13-dev-armhf-cross libgfortran-13-dev-i386-cross libgfortran-13-dev-ppc64el-cross libgfortran-13-dev-riscv64-cross libgfortran-13-dev-s390x-cross libstdc++-13-dev-amd64-cross libstdc++-13-dev-i386-cross gcc-13-cross
libasan8-amd64-cross libasan8-i386-cross libatomic1-amd64-cross libatomic1-i386-cross libgcc-s1-amd64-cross libgcc-s1-i386-cross libgfortran5-arm64-cross libgfortran5-armhf-cross libgfortran5-i386-cross libgfortran5-ppc64el-cross libgfortran5-riscv64-cross libgfortran5-s390x-cross libgomp1-amd64-cross libgomp1-i386-cross libhwasan0-amd64-cross libitm1-amd64-cross libitm1-i386-cross liblsan0-amd64-cross libquadmath0-amd64-cross libquadmath0-i386-cross libstdc++6-amd64-cross libtsan2-amd64-cross libubsan1-amd64-cross libubsan1-i386-cross gcc-14-cross
Looking at a shorter dependency chain:
the first of these, libc6-dev-amd64-cross is an Arch: all package:
$ rmadison -s oracular libgfortran5-ppc64el-cross
libgfortran5-ppc64el-cross | 14-20240412-0ubuntu1cross1 | oracular/universe | all
libgfortran5-ppc64el-cross | 14.1.0-1ubuntu1cross1 | oracular | all
$
It has libgfortran-13-dev-ppc64el-cross as a revdep, which is:
$ rmadison -s oracular,oracular-proposed libgfortran-13-dev-ppc64el-cross
libgfortran-13-dev-ppc64el-cross | 13.2.0-25ubuntu1cross1 | oracular | all
$
Its revdep is gfortran-13-powerpc64le-linux-gnu:
$ rmadison -s oracular,oracular-proposed gfortran-13-powerpc64le-linux-gnu
gfortran-13-powerpc64le-linux-gnu | 13.2.0-23ubuntu4 | oracular | ppc64el
gfortran-13-powerpc64le-linux-gnu | 13.2.0-25ubuntu1 | oracular-proposed | ppc64el
gfortran-13-powerpc64le-linux-gnu | 13.2.0-25ubuntu1cross1 | oracular | amd64, arm64, i386, s390x
$
component-mismatches does not want to demote gfortran-13-powerpc64le-linux-gnu, but DOES want to demote libgfortran-13-dev-ppc64el-cross.
