/usr/share/doc/libkf5activities5-dbg/changelog.Debian.gz is in libkf5activities5-dbg 5.18.0-0ubuntu1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/libkf5activities5-dbg/../libkf5activities5/changelog.Debian.gz