Consider purchasing a Blu-ray or DVD copy of the movie. This supports the creators and allows you to have a high-quality version of the film.
Free downloads often have "line-in" or low-bitrate audio, ruining the immersive soundscape created by composer Simon Franglen. Conclusion
using that search term, as websites offering "free" downloads of copyrighted movies in .mkv format are illegal and frequently contain malware.
These downloads are typically "locked" to the app for copyright protection and cannot be moved to a separate USB drive as a raw .mkv file. A Warning on "Free" Downloads