Male protagonist is a lab/vat grown human, with a birthmark on his face where it rested against the vat during gestation. I think there was a slur or maybe just a common term for people like himself.
Initially set on a human colony planet where the atmosphere is unbreathable outside the habitat he lives in with other laborers.
He is early killed when a military recruitment ship lands near him while he's outside operating mining? equipment.
He gets recruited into the military where a female rival (who becomes his friend) from a high-status military family thinks less of him due to his lack of experience.
The military uses simulation/VR to train recruits on power armor/exosuits. The power armor is central to the war effort and maybe even be referenced in the title but I cannot remember for sure.
The ship both characters are on is shot down at some point over a planet occupied by a rebel force the military has been suppressing.
I think I found this book on Amazon at some point but I have unable to find any evidence of it in my purchase history.