Why can't I bake any kind of functional normal map? I first noticed this issue when trying to bake a sculpted base mesh man to a retopologized one. I can't seem to achieve any kind normal bake that works at all. I've tried following multiple step by step baking guides on Youtube as well as the instructions in the Blender manual itself.
I've tried baking everything from the most complex shapes to smooth shaded high to low poly spheres. I've even tried exporting both high and low poly meshes to Xnormals for a different result with no luck. I'm sure its something simple and obvious, but I have been struggling with this for months. I prepared this hansom devil to demonstrate my problem.
 
This is the .blend file if you want to take a look.
Switch from Blender 2.8 to 2.7 or 2.9, because 2.8 may be buggy with regard to baking.

Create a new image for the normal, enable the 32 bit Float option:




Your bake Extusion value is much too high, bring it back to 0.1 (or give your Ray Distance a value of 0.1):



In the Shader Editor, use a Normal Map node, not a Bump node.



Bake:


The low-res without the Normal map:

With the Normal map: