I've done almost this exact same thing. Flew UA to France for a long-term stay but arrived in a different country (Germany).

Nobody at UA even batted an eye. Didn't even look for my visa. As far as they cared, I was a US citizen flying to the Schengen zone and it didn't need to be more complicated than that.

For that matter, the immigration agent at FRA didn't even look up from his desk as he stamped my passport.