My current interest is back to Egypt again in search of the megalithic builders. I diverted attention to the Nubian influence / kushite kings. Their pyramids/buildings what is left looks far inferior to the Egyptian stone works however there is one very interesting detail.
Their sarcophagus are huge and of granite and of similar design/size to the Serapheum sarcophagus. It shows they did have the capability to deliver Osireion style granite workings. (or re-purposed older ones is also still possible)
Image / sarcophagus of King Aspelta. (Note how the lion opposes Annubis instead of two lions.)