I can stream MKV’s to the Plex Web app, however, Plex falls on its face when streaming the same content to the Plex native Android app.
Currently, it shows a rather generic error message when I try to do this. I suspect this is a compatibility issue regarding transcoding to Android supported formats. But I’m not even sure of the root cause, because of the error obfuscation.
This applies to most any foreign language media such as archived anime footage. MKV is the premier, standard format for this kind of subtitled/dubbed content. But Plex is bad at transcoding MKV files to Android as well as other smart TV Plex apps. It’s also bad at transcoding MKV files when selecting the cache on device option in assorted Plex apps.