Some streaming services offer high-quality video downloads, including in MKV format. Netflix, for example, allows downloads of select titles in high definition.
Specifies the preferred file container. is popular for high-quality video because it can hold multiple audio tracks, subtitles, and high-definition video streams in one file. index of mkv 300 high quality
If you're looking for an index or a list of MKV files with high quality (often considered to be at least 1080p or 4K), here are a few general thoughts on how to approach this: including in MKV format. Netflix