/usr/lib/x86_64-linux-gnu/liblightdm-qt5-3.so is in liblightdm-qt5-3-dev 1.18.1-0ubuntu1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/liblightdm-qt5-3.so.0.0.0
/usr/lib/x86_64-linux-gnu/liblightdm-qt5-3.so.0.0.0