there are lots of low recoil buckshot loads for the 12 and 20 ga made for law enforcement that can be found in well-eqipped gun shops and police supply houses.
My 12 ga remington 870 is loaded with Hornady TAP shotgun shells.
Keep in mind who the recommendations are for. Even low-recoil 12 ga has a pretty serious kick to it. When it comes to home defense 500 yard shots sound a little unlikely to me also. How do you explain to an LEO that you felt your life was in danger when you’ve dropped an illegal alien almost two football fields away from your house?