And here is a website with a whole list of Black/African Saints. And here’s a webpage with just fifteen if you want to start out with a less overwhelming number. This site (which I also link below) has a good number of the most well-known early African Saints.
I think people often don’t realize that certain Saints are Black because they are, alas, whitewashed in most images of them (Augustine being a prime example of that). So when you click the links above, you’ll probably take one look at the images included on webpages and go “lol this guy’s not black!” It can be frustrating, but luckily non-whitewashed art is out there – it’s usually very ancient or very contemporary. I’ll include some here.
Moses the Black (source), Thea Bowman (source), Martin de Porres (source)
Africa played a key role in early Christianity, and it’s a shame that history tends to be ignored by Christians today. As this webpage attests, three of the earliest popes were African! as were many martyrs. One place you can go to look into that is the website of the Center for Early African Christianity.