/usr/lib/x86_64-linux-gnu/libfftw3l_mpi.so.3 is in libfftw3-mpi3 3.3.3-2ubuntu3.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libfftw3l_mpi.so.3.3.2
/usr/lib/x86_64-linux-gnu/libfftw3l_mpi.so.3.3.2