Okay, a 1000 years spanning 450 AD up to 1450.
it's interesting that you exclude the Iberian peninsula. They're Europeans. You also add in the Muslim faith. They're also Europeans. And that you parse out that "a few rare exceptions" of Christians owning slaves. So, what you mean Northern Europeans from the French/Germanic area that also includes the British islands.
But bad news. They had slavery too.
Okay. The Visigoths were a germanic people. One of the Gothic tribes that migrated/settled in from the Balkans to the German/Franco/Iberian area by the 300s. That's when their conversion to Christianity began. They sacked Rome in 410. They were a powerful force in the region until the 900s.
They were European. Christian. And they had slaves. Until the 900s. They even wrote it down in their laws. See the Visigoth Code.
But that's just 1 group, right? No. There are others.
The Welsh also had slavery. The Cyfraith Hywel (medieval Welsh laws) only applied to Free Welsh Men, and specifically did not apply to slaves. You don't invent an entire code of laws, write them down, and specifically say "these don't apply to slaves" if you don't have slaves.
The Kingdoms of Moldavia and Wallachia had slavery until the 1400s. (That's modern day Romania region).
But we're not done.
Those White Christian Northern Europeans decided they needed to "free" Jerusalem from the people who lived there. Upon taking over, they inherited the local slaves. Along with the city of Acre. It was the largest city in the region. And it had an slave market that made tons and tons of money. They didn't shut it down. They kept it going. For centuries. It's from this era that the idea of "Christians can't own Christian slaves" comes into existence. It was fine to own non-Christians. But not Christians.
It was in the 1200s when Pope Gregory said, "hey, all these Muslims & Jews are converting to Christianity to get out of being slaves. You don't have to free them if you don't think it's sincere."
And if you're thinking "oh, but that happened in a different part of the world, NOT IN THE PHYSICAL AREA OF EUROPE!!!" That's a ridiculous level of parsing. Christian Kings and the Church fully endorsed and profited from slavery. Their proxies in the crusader kingdom owned and operated slave markets.
If you own slaves in Acre but live in Paris, you're still a slave owner.