What solution does SpaceX plan so to make it possible for the crew to get out from Starship on other planets, considering the cabin's elevation? Will they use some kind of rope ladder?
No. Rope ladders would not be very practical or safe. They might use an electric hoist as a back up, but the plan is to use a lift to reach the surface. One possible solution is shown in the SpaceX Starship user guide (see bottom of last page). https://www.spacex.com/media/starship_users_guide_v1.pdf This is not the only configuration possible, but is indicative of what they plan