무인기 (non-human device) is a term that is used commonly in South Korean military alongside 드론 (pronunciation of drone written in Korean), so it’s not too weird to see it there. They tend to avoid borrowed words for some reason.

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I’m Korean, and while I can’t make out what it exactly says because of the handwriting, some words are recognisable and the translation in the OP’s post seems accurate. I don’t see anything they missed out either.

I don’t have a Telegram account, so I can’t see other contents.