/usr/lib/x86_64-linux-gnu/libnetfilter_conntrack.so is in libnetfilter-conntrack-dev 1.0.4-1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libnetfilter_conntrack.so.3.5.0
/usr/lib/x86_64-linux-gnu/libnetfilter_conntrack.so.3.5.0