Unreal Impostor Shader 4.27

Drop this file into your unreal project (only version 4.27 works)
if you use older engine versions you have to open the shader editor for this material in an 4.27 project and copy the nodes over to a new material in your older UE4 version.

Unreal Impostor Shader 5.0

drop the file into your unreal 5.0 project.

ImpostorBaker2.0.1

Install it like any other addon in Blender