/usr/lib/x86_64-linux-gnu/libArcus.so is in libarcus-dev 3.1.0-1ubuntu1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libArcus.so.3
/usr/lib/x86_64-linux-gnu/libArcus.so.3