Do you mean like this?
unrealsensei has a long 3 part tutorial on this
like 2 hours
You have to use tiled textures. The larger an object is the more the texture sample will stretch over the surface, and landscapes are by definition very big…so you either need a very large texture sample (huge memory cost) or accept a blurry landscape.
The way around this is to use a tiling texture but to hide the tiling pattern, which is what basically everybody does. There are a few approaches to this (e.g. cell bombing, using seamless textures, lerping between multiple layered samples using a mask, etc.). The UESensei video above covers one of these techniques I think.
At the distance painted, the landscape doesn’t have to be a landscape…
In the specific scene it may not even have ever been a landscape…
Yes, could even be a skybox.