Say there is a relatively advanced and centralized state in and around OTL Capetown and Natal in South Africa. I don't know, Arabian migrants, Moroccan missionaries, a diaspora of Zheng He's crew or some other Asians migrated and set up shop. How might this affect European exploration to the East? Possibly gunpowder weapons in small, antiquated quantities - bought from your choose or Arab trader along the East African coast - and at least some comparable (numbers, if not tech) naval vessels.
I have no doubt they would be essentially Conquistador'd upside the head, to one degree or another and varied levels of success depending on other factors, but really... Are these guys absorbed, vassalizes, sold to slavery, or somehow wiped out?
And which nations would be most likely move into the area in strength? Does this make more interest in the Dark Continent - thus diverting some from Americas? What happens?