I didn't know that I had an app on my Android device - YouTube Music - which is capable of playing midi. I was quite surprised.

I've had other Android devices over the years which had other media players. I can't remember which ones played midi, if any. I mostly used them to play mp3, aac, mp4, etc.

Also midi files vary - some are served from the webserver with the wrong file extension or mime-type. So you might be able to play some and not others.