The landscape is all dark

It is the most common problem and it is related to the Runtime Virtual Texture (RVT) needing to be set up properly and there are multiple things to look at.

1) In your scene, there are 2 "Runtime Virtual Texture Volume", make sure their bout match the size of the world and that they have a Runtime Virtual Texture installed, one is for the color and the other for the height.

2) Check your landscape. In it, there is a Virtual Texture section, and it is supposed to have the 2 same RVTs you want to use.

3) The original material uses Runtime Virtual Texture but since the height of the world often changes, the bounds can end up lower than the max height of the current RVT leading to a black map/area like the screenshot below.

The fix is easy, simply manually increase the Z scale of both Runtime Virtual Texture in your scene. Don't forget to uncheck the "proportional" scale otherwise, it will stretch your texture. See the video below for an example.