If we assume you mean knowledge gained by archaeology/anthropology (in their earliest iterations), for the most part the "we" in this question is essentially the French, since the French were most involved in Egypt prior to hieroglyphic decipherment. Specifically Napoleon Bonaparte and his scientists who were commissioned to study Egyptian history and monuments while he was in the country. The result of the years of study (1798-1801) was published in the book "Description de l'Egypte" (find it here in French. I know I've downloaded an English translation of at least one of the volumes (or maybe it's just a collation--it's been a while since I dealt with it) but I can't find it quickly. If you want it, message me and I'll see what I can do.

However, long before Napoleon there were "contemporary" sources who wrote about the Egyptians--sources whose observations misinformed the study of Egypt for hundreds of years. For example, Herodotus, a Greek historian who lived in the 5th century BCE, ( see here for a translation of his writings on Egypt ) was one of the biggest culprits in conflating Egyptian gods with Greek. Essentially I mean that Egyptian gods, despite having their own names, were often given the name of their closest Greek counterpart. For example, under "42" on this document:

"Therefore the Egyptians give their statues of Jupiter the face of a ram: and from them the practice has passed to the Ammonians, who are a joint colony of Egyptians and Ethiopians, speaking a language between the two; hence also, in my opinion, the latter people took their name of Ammonians, since the Egyptian name for Jupiter is Amun."

Another Greek historian is Diodorus Siculus (1st century BCE). Check out Volume 1 here. Again, although there are good clues to be gleaned here regarding the lives of the ancient Egyptians, the source is not to be taking completely without a grain of salt.

I haven't included any secondary sources here, but would be happy to provide recommendations if you need them. I personally like digging into the primary sources, though!