Same problem here on my 2019 Sierra Denali with 5k miles on it. Early morning backing out of the driveway she squeals like a b*tch, and if im driving under 15 mph and brake she'll squeal too. This shouldn't be an issue on a 60k+ truck. I took the front brakes apart cleaned them up greased the pins and anti-seized the pads, helped for a few days but now back to the squealing. I also have burn marks on the rotors. Going to the dealership this week to see what they can do. Thank god the dealer I use is always amazing with stuff like this but I feel its more of a mechanical issue with the brake system seeing how many of you are suffering from the same problem.