Brought my UE4 jungle pack over to Unity, but not just with the standard shaders. It does include those, but I also rebuilt most of the Unreal materials in the HDRP shader graph. First time trying out the new render and post-process settings too; Unity is looking a lot better!
The Unity pack can be found here: https://www.assetstore.unity3d.com/#!/content/162908
The UE4 version is here: https://www.unrealengine.com/marketplace/en-US/product/alien-jungle-set
The assets themselves were made with a mix of Maya, Houdini and Substance Designer.
The Substance files are also available: https://undertow.artstation.com/store