You're right that persons is barely used, and generally only in techincal jargon. The normal plural of person is people, and you should basically always use it.

But there's also a singular word people, which is the one being used here. It refers to a large group of people with some sort of national or ethnic ties, and is popolo in Esperanto. Since this particular word people is singular, you can add an -s to make it plural, which is why it's peoples in this example.