Simple material (diffuse nodes mixed through a "Pointiness" factor) does not work in EEVEE I have a material that works very well in Cycles, but nothing appears in EEVEE. Where does this problem come from? Is there any way to fix that?
Not all shader nodes that work with Cycles work also with Eevee. The Geometry "Pointiness" socket doesn't, as well as the other "geometry-aware" nodes like Ambient Occlusion or Bevel.

Here is a reference about node support: https://docs.blender.org/manual/en/dev/render/eevee/materials/nodes_support.html

If your mesh isn't animated, you can bake Pointiness using Cycles and then use it in Eevee: 


Unwrap your mesh,
connect the end of the Color Ramp to an Emission shader and the Emission Shader to the Material Output
Add an Image Texture* node, with a blank, new image, and leave it unconnected, but selected
Bake in "Emission" mode (while using Cycles)
Save the baked image
Use the baked image as a Texture* for the Mix factor in Eevee


* if you have multiple UV maps, the image textures must always have their Vector input connected to the correct UV Map node.