I put up a SS here: Custommaterial and importmesh as I found a bug with pbrcustommaterial.
Its a very early prototype and the splatmap isn’t done yet as the terrain assignments are not yet complete. My use case is all square tiles hence the tiled look. I don’t see any obvious edge seams from my side. Using 1k splatmap, diffuse, normals, roughness and macro texture for testing purposes right now.
Hope it helps.