I installed the painted flares on a 2020 Sierra, few things I learned. Passenger side I took the inner fenders out to get to the back of the clips..... don’t waste your time doing this. The back ones have several of the clips enclosed anyway. In the end here is what worked for me.
Start by pulling the lower rear corner of the trim, pull it off enough (maybe 3-4 clips) pulling very hard.....
once you have it off enough that you can look in and see the next clip, use a flat screwdriver, be sure to press the tip away from the finished paint in case you slip, and put the screwdriver between the flare and truck on one side of the clip. The clips have wings that snap into the hole. You really only need to press one wing to get the clip to release. With a steady outward pull, the clip will pop out still attached to the trim piece damage free.
once you have about a 1/3 of the flare pulled away, pull it down causing the clips on the top to slide out of the trim. NOTE - the front uses different clips where it attaches to the bumper (front) and they will not slide out, again use the screwdriver to depress the wings of the clips to release them without damage. The back flare will easily slide of the clips as you pull down for the top and towards the rear of the truck for the front 1/3.
the clips will stay attached to the truck. I used standard pliers to pull outward on the existing clips while using the screwdriver to depress one side of the clip releasing it damage free.
it will only take you about 10 minutes to remove each flare
when you install the new ones just make sure the inner fender is between the lip of the flare and the truck and snap it into place
total is about an hours project.
this was done on a brand new truck, so I imagine with some age the clips may be more apt to break. None broke on me.