/usr/lib/x86_64-linux-gnu/libdap.so is in libdap-dev 3.15.1-7.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libdap.so.17.3.1
/usr/lib/x86_64-linux-gnu/libdap.so.17.3.1