/usr/include/mlt/ is in libmlt-dev 6.0.0-2.
This file is owned by root:root, with mode 0o755.
..
/usr/include/mlt/framework/
/usr/include/mlt/framework/mlt.h
/usr/include/mlt/framework/mlt_animation.h
/usr/include/mlt/framework/mlt_cache.h
/usr/include/mlt/framework/mlt_consumer.h
/usr/include/mlt/framework/mlt_deque.h
/usr/include/mlt/framework/mlt_events.h
/usr/include/mlt/framework/mlt_factory.h
/usr/include/mlt/framework/mlt_field.h
/usr/include/mlt/framework/mlt_filter.h
/usr/include/mlt/framework/mlt_frame.h
/usr/include/mlt/framework/mlt_geometry.h
/usr/include/mlt/framework/mlt_log.h
/usr/include/mlt/framework/mlt_multitrack.h
/usr/include/mlt/framework/mlt_parser.h
/usr/include/mlt/framework/mlt_playlist.h
/usr/include/mlt/framework/mlt_pool.h
/usr/include/mlt/framework/mlt_producer.h
/usr/include/mlt/framework/mlt_profile.h
/usr/include/mlt/framework/mlt_properties.h
/usr/include/mlt/framework/mlt_property.h
/usr/include/mlt/framework/mlt_repository.h
/usr/include/mlt/framework/mlt_service.h
/usr/include/mlt/framework/mlt_tokeniser.h
/usr/include/mlt/framework/mlt_tractor.h
/usr/include/mlt/framework/mlt_transition.h
/usr/include/mlt/framework/mlt_types.h
/usr/include/mlt/framework/mlt_version.h