I know this isn’t that important to ask but the reason is people use Islam especially white supremacist to say that black people aren’t really African or black and that they are Arab it’s just apart of a racist trope to say Africans weren’t and still aren’t capable of greatness I know there is a such thing as an African muslim but I’m asking.
The religion of Islam came about in roughly the seventh century common era. Therefore, any African Civilization that was prominent during the Ancient era would not have been an Islamic state, and or Caliphate because the religion did not exist yet.
Just a few examples: Aksumite Empire Kingdom of Makuria Egypt up until the end of the late period, where just about every major religion tried to have a say.
Sources:
(Kingdom of Makuria) Adams, William Y. (1977). Nubia: Corridor to Africa. Princeton: Princeton University. ISBN 978-0-7139-0579-3
(Egypt) Assmann, Jan (2001) [1984]. The Search for God in Ancient Egypt. Lorton, David transl. Cornell University Press. ISBN 0-8014-8729-3.