I haven't been able to find any information on this either on AskHistorians or elsewhere, probably because of the difficulty involved in understanding contemporary ethnicity around the world, let alone in understanding ethnicity as it applied to people in the past.

With that said, my understanding is that Egyptian identity in the modern era is pretty complicated and involves different ideas about their status as Arabs, as Muslims (and as Christians), and as heirs to a 5000 year old civilization, but that they refer to themselves as Masreyyin (or something along those lines).

This looks like more of a national, i.e., 21st century style nation-state-citizenship based identity than anything else. I also understand that ethnicity and other types of group identity take many different forms across the world!

But assuming Masreyyin serves as the primary identity of the people of Egypt apart from their religious identities, when did this take effect? I've read that Ancient Egyptians referred to themselves as "People of Kemet" and I believe modern Copts refer to themselves as Niremenkimi.

TL;DR: Did the Islamic conquest of Egypt transform local identity from Niremenkimi / Rmt-n-kmt to Masreyyin? How long did the process take? What did this transformation look like?

Thank you for reading and answering my long and probably difficult question!