The Egyptian Pharaoh Akhenaten, (Amenhotep IV), father of Tutankhamun, came to this conclusion during his reign as Pharaoh and was a monotheist, worshipping Aten, the sun disk. He was not a dualist, he was a monotheist. He did not permit symbols or images of the Aten. He tried to eliminate the old religious system and built a city for himself and his religion. He ruled for 17 or 18 years and was succeeded by his son, who under the influence of the priests of the old system, returned to the old ways. I do not know if at this time there was any contact between the Israelites and the Egyptians, but monotheism was present in the Egyptian culture for a short period of time. in the 14th century BC.
Here is an article from Biblical Archeology Review discussing him, and also mentioning the possible influence on Moses, which I believe, was rejected by most archeologists.
biblicalarchaeology.org/daily/ancient-cultures/ancient-near-eastern-world/akhenaten-and-moses/
You will note that the monotheism developed differently among the Israelites, developing over a long period of time, whereas Akhenaten’s was a sudden development which he forced on the people, but nevertheless was monotheism.
I am no scholar or archeologist, so this is as far as I can elaborate. I have subscribed to BAR for a number of years, and this is not the first time this subject has come up.