/usr/share/doc/remmina-plugin-xdmcp/changelog.Debian.gz is in remmina-plugin-xdmcp 1.2.0-rcgit.29+dfsg-1ubuntu1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/remmina-plugin-xdmcp/../remmina/changelog.Debian.gz