There are definitely people who are enslaved in the UAE under the Kafala System. It’s unclear to me how widespread it is, but it does happen. When I was there, I personally met a woman on Tinder, and on our date she told me she had been forced into prostitution by the person who brought her to the UAE. She had to earn tens of thousands of dollars to get her passport back from him.
This is absolutely illegal and you can get your passport back within a day or two by just calling MOHRE.
A decade ago this stuff may have been more common, but the government has cracked down heavily to the point that it doesn’t exist any more than it does in Europe.
You’ll find more slaves per capita in the US where prisoners are widely used as actual slave labor.