Slavery in medieval Europe was widespread. Europe and North Africa were part of a highly interconnected trade network across the Mediterranean Sea, and this included slave trading. During the medieval period (500–1500), wartime captives were commonly forced into slavery.
About ten percent of England’s population entered in the Domesday Book (1086) were slaves, despite chattel slavery of English Christians being nominally discontinued after the 1066 conquest.
Rebranding "slaves" as "serfs" was a smart move, but a Rose still has thorns when called by other names.
Just because:
The Church prohibited the export of Christian slaves to non-Christian lands, for example in the Council of Koblenz in 922, the Council of London in 1102, and the Council of Armagh in 1171.
doesn't mean that there were no slaves within Christian lands, it just meant there wasn't a profit to made trading across those borders (for Christian slave merchants) ...
As a result, most Christian slave merchants focused on moving slaves from non-Christian areas to Muslim Spain, North Africa, and the Middle East; and most non-Christian merchants, although not bound by the Church’s rules, focused on Muslim markets as well.
I'm not seeing any support for your "practically no slaves" assertion.
I am reading explicit mention of ongoing Christian slave merchants post Roman Empire .. which goes to my point that aside from rebranding and cross border regulation the post Roman Christians took a long long time to outright ban slavery.
So ... no support for an assertion I did not make? That seems .. random.
But a contradiction of the claim that you made?
Common knowledge would have it that slavery did not exist in medieval Europe.
However, there is a thriving body of scholarship which demonstrates that slavery was practiced widely in various forms in Europe during the Middle Ages, alongside captivity, serfdom, and other types of unfreedom.
[ What "common knowledge" claims, where that came from, ... ]
Yet into the 14th and 15th centuries, medieval Europeans continued to own slaves, trade in slaves, and enslave each other as well as non-European others. They used slaves for agricultural and artisanal labor as well as domestic, sexual, reproductive, and military service
( from an assistant professor of history whose research interests covers practices of slavery in the medieval Mediterranean, particularly the slave trade from the Black Sea to the markets of Cairo, Genoa and Venice during the thirteenth through fifteenth centuries. )
Someone whose day to day existence was mostly under their own control, so long as they stayed tied to the land and produced. Both slavery and serfdom are terrible, but they are not the same.
From the perspective of industry though, serfdom is a purely agricultural institution.
They couldn't be sold. They had rights. In general the classic school hierarchy of emperor, vassals, valvassori (dunno in english), valvassini (also don't know in english), serfs has been debunked.
Rich people might have a couple, but in the middle age slave labour was negligible.