So, I’m trying to get enviroment reflections in Unity 6000.0.23. I was trying to sample unity_SpecCube0 as always (I’ve checked it works for unity 2021), but it returns black color and nothing more, any ideas on how to get environment reflection samples properly? Same goes for unity’s brdfs 
btw, also will mention shadergraphs node “Ambient” also returns here balck color for any value.
Have you found a solution yet? I’m facing the same problem.
I had the same problem, but it wasn’t happening in the editor or on all of the platforms I built it on.
It seems that sampling unity_SpecCube0 in anything other than a renderer in a scene is undefined behaviour.
[URP][Lighting] The skybox doesn’t render after changing the settings of the Material when using the URP Render Pipeline
unity_SpecCube0 is not set when there are no GameObjects in the Scene
“In summary, uniforms like unity_SpecCube0, unity_SHAr, etc. are only meant to be used in shaders applied directly to a renderer in the scene. When used elsewhere, they are in an unspecified state. If your usecase demands feeding a cubemap to your skybox material, you can set it manually using Material.SetTexture on RenderSettings.skybox, or by using Shader.SetGlobalTexture.”