/usr/lib/x86_64-linux-gnu/libnautyS1.so.2 is in libnauty2 2.6r7+ds-1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libnautyS1.so.2.6.7
/usr/lib/x86_64-linux-gnu/libnautyS1.so.2.6.7