/usr/lib/x86_64-linux-gnu/libct.so is in freetds-dev 0.91-6.1build1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libct.so.4.0.0
/usr/lib/x86_64-linux-gnu/libct.so.4.0.0