Sudan was one of the last places conquered by the arabs, and one of the last places in which islam spread in general (with Alodia falling in the 16th century). In the country had a significant native (subsaharan) african population.
Yet right now it seems like arab is the dominant ethnic group by far, with the majority of the population identifying as arab. Many ethnic groups like the Beja are largely arabised and some claim arab descent (even in cases where it may not be supported genetically). The nubian people have a smaller geographic spread (with old Alodia being entirely arab), and only an incredibly small minority still is coptic, contrasting Egypt where a significant coptic minority remains. Darfur is the notable outlier, but has been the subject of multipule genocides in the 21st century.
Even after the fall of the nubian kingdoms, the funj sultanate for a while did not strictly enforce orthodox Islam.
Are there any people from Sudan here?