/usr/lib/x86_64-linux-gnu/libfko.so is in libfko2-dev 2.6.0-2.1+b1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libfko.so.2.0.0
/usr/lib/x86_64-linux-gnu/libfko.so.2.0.0