It can be one of 6 normal maps used in landscape, base name is MultiTextureNormal0Sampler in old skyrim. What i see in shaders, most of skyrim se with sampler 7 have very similar look as landscape shaders in old skyrim, so i think it's one of such maps.7: "MaterialLandscape: normal map" (???)
Don't remember anything like that and can't answer now, this need practical test in the game which objects have such sampler, i'll do this later.10: ProjectedNormalDetailSampler (???) ProjectedNormalDetail.dds
WorldMapOverlayNormalSampler do exist in old skyrim, but again better to test.13: WorldMapOverlayNormalSnowSampler OR LODBlendSampler (Skyrim 20 -> SSE 13) WorldMapOverlaySnow_n.dds -- "MaterialLandscape: LOD blend map"
PS: i'm busy with moving to live in another place, so can't work on mod very actively, so may start to work on your results after 11 nov or maybe sooner can't tell for sure yet.