Overall a good analysis. Notable: Europe generally banned slavery of Europeans in the Middle Ages, leaving Africa the primary source of commercial slaves - enslaved by their own - hence the subsequent racial associations.
End gets a bit squishy. Please ensure discussion of slavery doesn’t dilute the term by including “poorly paid with few options” which isn’t slavery (that’s a problem to address, but it’s not outright ownership of humans as disposable tools).
“poorly paid with few options” In China that can be ownership when you are forced into it and are given no choice about it whatsoever. Pay means nothing, even slaves got food, maybe some slaves got more than they are getting.
Europeans banned the enslavement of European Christians of the right kind—in the late Middle Ages there were Catholics enslaving Orthodox and vice versa, and both enslaving “infidels” (Muslims or pagans). Enslaving African blacks was only considered OK if they were “infidels” which most of them were—the Portuguese carried pagan Africans to Brazil but did not enslave the Catholics in the Kingdom of Kongo. Meanwhile the Muslims were happily enslaving anyone who was not Muslim, white or black, unless they were “protected people” (and in the case of the Turks even Christian boys living under Ottoman rule).