Like, why wouldn't people be interested in knowing that the African slave trade of the colonial period actually started with Jewish kids, but they all died in the African climate of Sao Tome, so the Portuguese started buying slaves from the Congolese, which they captured from neighboring tribes, to work the fields??
The post mentions Africa though, does it make a difference?
Well yes. The Ottoman empire during almost all of the colonial period was a serious powerhouse and major player; one where slavery was one of its major economic engines. And you can't really include any discussions about slavery in Europe without also including the Ottomans.
There is a trick to tracking it though. A lot of the relevant official records from the Empire don't track the movement of slaves or women.
If we're concerned about ethnicities, which we are here, the trick is they weren't. They would note the religion of slaves, and had a tendency to just lump all Africans as Muslims or Arabs(Arap). The documents we have that make notes about sub-Sarahan African slaves comes primarily from British or French people traveling through the markets or cities.
For a numerical example: half of the slaves in markets in Ottoman Cyprus between 1590 and 1640 were sub-saharan African. Of the remaining half, almost half of those were Russian, the rest Greek and Slavic.