/usr/lib/x86_64-linux-gnu/libmlt.so is in libmlt-dev 6.6.0-1build1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libmlt.so.6.6.0
/usr/lib/x86_64-linux-gnu/libmlt.so.6.6.0