Hi Mark,
When I was first reading about Hip Replacements, I saw a lot of “treadmill running” references. Flat consistent surfaces were the norm. But as you can see with this site, we have guys running trail races, road races, skiing, and everything in between. Initially, I would say stick to the soft flat if you can. But as your hip get stronger, there really should be no reason why you can’t live your life normally and just run. The key is to listen to the hip. It will guide you on this journey.
Hip Brother Tom.