/usr/lib/x86_64-linux-gnu/liballegro_dialog.so is in liballegro-dialog5-dev 2:5.2.3.0-1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/liballegro_dialog.so.5.2
/usr/lib/x86_64-linux-gnu/liballegro_dialog.so.5.2