imported photogrammetry seems overly bright compared to the maps. Knowing UE4, I would guess you have the specular pin open (=1). Connecting a constant with value 0 is better to show diffuse colors of the photogrammetry textures.
Hello @ILikeHighEndGraphics ,
We will likely expose some material override capabilities in the future, but in the meanwhile you may want to experiment with directly editing the materials in the Cesium for Unreal Content folder.