Some breeds of dog are bred to run. A fine example is my Australian Working Kelpie, Guinness. He was raised on a sheep station, and those dogs are mustering sheep in the paddock from quite a young age. I started running with Guinness when he was just under 12 months old.
Some breeds have inherent orthopaedic problems, and in those breeds, I’d hold off a while until their body is more physically mature.