/usr/share/doc/libkasten3okteta1gui1/changelog.Debian.gz is in libkasten3okteta1gui1 4:17.12.3-0ubuntu1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/libkasten3okteta1gui1/../libkasten3core3/changelog.Debian.gz