I haven't seen one of those "folding step license plate brackets" in years. Possibly JC Whitney would have them, but you'd run the risk of getting a weekly catalog and daily flyer for the next 12 months if they get your address....
On my 2015 F250 there isn't any "good place" to attach a step. The license plate bracket is attached to the top and bottom chrome bumper with 4 small screws that probably wouldn't support a 200 pound man on a "levered step" that folds down. I'm over 6' and still have problems getting "tall enough" to access the engine, so I just slip my foot into the bumper, next to the towing hook (on each side of the license plate) and use the top of the grill near the hood latch as a hand hold to pull myself up.