In PC ,RHICreateTargetableShaderResource2D will create SeparateTarget and ShaderResource, and after basepass resolve depth from TargetableTexture to ShaderResourceTexture.
But in mobile preview, it does not resolve depth.So the ShaderResourceTexture is empty.
1.Create a PostprocessMaterial
2.Add a SceneDepth Node, out put as color
3.Set the PostprocessMaterial to PostprocessVolume.
4.Change to Mobile Preview
There's no existing public thread on this issue, so head over toAnswerHub just mention UE-64245 in the post.