Hello.
I was trying to use RenderTarget or Static Texture made from RT and the result was not correct, so it is not the way
BUT!
I use RenderTarget variable in blueprint and export calculated normal with blueprint node ExportTexture and save as *.HDR and then I open file in Photoshop and set RGB/8. After that I import new texture into an engine and it work fine.
Make notice, that pre-baked normal map (that I use as basis) compression was set to HDRCompressed.
Something like that:
*White arrows means it is exactly the same variable.
** DrawMaterialToRenderTarget used for preview purpose only. It doesn’t work correctly in Editor viewport.