/usr/lib/x86_64-linux-gnu/libdunegrid.so is in libdune-grid-dev 2.4.1-1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libdunegrid-2.4.1.so
/usr/lib/x86_64-linux-gnu/libdunegrid-2.4.1.so