Terrain mode is still there, you just have to type Terrain in the search bar, and it'll switch the view. Then X out of the search to return to the normal map view. Otherwise, if you click the input box, you should get a terrain button in one of the many expanding boxes.
I don't know who came up with the above concept for switching modes, but it's absolutely awful.
I don't know who came up with the above concept for switching modes, but it's absolutely awful.