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, also shown below).
This is not the only configuration possible, but is indicative of what they plan.
Starship was designed from the onset to be able to carry more than 100 tons of cargo to Mars and the Moon. The cargo version can also be used for rapid point-to-point Earth transport. Various payload bay configurations are available and allow for fully autonomous deployment of cargo to Earth, Lunar, or Martian surfaces with one example shown in Figure 7.