/usr/lib/x86_64-linux-gnu/libgeant321.so is in libgeant321-2-dev 1:3.21.14.dfsg-11build1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libgeant321.so.2_gfortran.2005
/usr/lib/x86_64-linux-gnu/libgeant321.so.2_gfortran.2005