Your first source is a costume-designer with a very obvious agenda talking about European history. She sources little of her statements, some of them with actual pieces of fiction (including anachronistic art).

Your second source basically amounts to “contemporary writers didn’t say there weren’t Africans in Europe *wink*”. It’s written like your typical ancient aliens stuff.

The third describes more the spread of influence than the actual populace, and is written by Runoko Rashidi, an afrocentrist “historian” who liked to claim historical figures were black in spite of when evidence to the contrary existed. These folks are colloquially known as “hoteps” in some circles.

Obviously given the nature of humans, cultures, and empires, it is likely some amount of black Africans ended up in Europe. That said, given historical records as understood by actual historians, we have reason to believe there were not many of them. Why does it even matter though? What would black Africans being in Europe even prove?