It’s pronounced “Carney”. I grew up in Nebraska. Competed against them in athletics, and my brother graduated from college there. Anyone who states it’s pronounced any other way is simply incorrect.
Some current residents new to this country may be pronouncing it differently, as in the case of Kearny, NJ.
They’re pronouncing it so as to rhyme with “Bernie”. And nobody they talk to on a regular basis is contradicting them.