/usr/share/doc/kde-config-sddm-dbg/changelog.Debian.gz is in kde-config-sddm-dbg 4:5.5.5-0ubuntu1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/kde-config-sddm-dbg/../kde-config-sddm/changelog.Debian.gz