/usr/lib/x86_64-linux-gnu/libKScreenLocker.so is in kscreenlocker-dev 5.5.5-0ubuntu1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libKScreenLocker.so.5
/usr/lib/x86_64-linux-gnu/libKScreenLocker.so.5