/usr/share/doc/libhdf5-mpich-10-dbg/changelog.Debian.gz is in libhdf5-mpich-10-dbg 1.8.16+docs-4ubuntu1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/libhdf5-mpich-10-dbg/../libhdf5-mpich-10/changelog.Debian.gz