/usr/share/doc/strongswan-plugin-eap-gtc/changelog.Debian.gz is in strongswan-plugin-eap-gtc 5.1.2-0ubuntu2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/strongswan-plugin-eap-gtc/../libstrongswan/changelog.Debian.gz