I was able to get UFE running in Unity 2018.1.0f2 after commenting out:
Assets/UFE/Editor/CharacterEditorWindow.cs(1158,104): error CS0143: The class `UnityEngine.AudioClip' has no constructors defined
Assets/UFE/Editor/MoveEditorWindow.cs(1969,101): error CS0143: The class `UnityEngine.AudioClip' has no constructors defined
Doesn't appear to cause any real problems, but I have not done any serious testing with it.
Note, I made a fresh project and re-imported UFE from the Asset Store, if that makes a difference.