That's much the same as Firefox on my Android 7 tablet, except that tapping a link on GUEST's link
https://www.mfiles.co.uk/midi-files.htm
I get this:
screenshot (expires in 21 days)

Chrome is similar. But you may have told Android to download such files in the past and remember the choice.

That site, as mentioned earlier, serves midi files as audio/x-midi which I think is the one to use.