I remember having been told that the original Russian pronounciation
is "mi" (as in the word "mist") pronounced as one syllable.

aircraft is in Finnish always called "em eye" .

Interesting, since in German it has always been pronounced as you said
"Mi" (for English mist like you said).
I have never in my life heard a different pronounciation, which is funny
since I did a lot in the US (obviously those helis weren't talked
about).

I always wondered what the Mi means. Mil is the last name of the chief
developer, so why Mil Mi-26 instead of just Mil-26?