mkv is just a container and can carry video, audio, and other files. It’s true that VLC can play mkv files.
However, based on the file name, the content seems to be Atmos encoded. VLC will play this by passing it through, but it doesn’t decode Atmos and then it still needs an Atmos capable endpoint.
not sure you can play atmos the stream version, but I extract audio out of mkv’s with this tool (or a similar one - its been a while since i downloaded it and i am not on my home machine at the moment). Its great to have the audio from music dvd and blurays this way.