> Can you find true monopolies in the free market

Your definition of monopoly isn't what people are commonly talking about when they say "monopoly".

Granted, you have the correct definition, just not the colloquial one.

What people say "monopoly" what they are really talking about is industries captured by few big players. For example, grocery stores. There's not a true monopoly there but there is damage done by the fact that there's very little competition in that space. Both to consumers and product manufacturers. These big grocery chains use their leverage to get prices smaller chains can't compete with. Further, they have been trying to consolidate (see Kroger Albertsons merger) to further exert anti-trust behaviors.

A clear example of the damage done by this sort of hyper consolidation is what's happened to the memory market. Multiple times the 3 big players have been hit with anti-trust lawsuits because of the price fixing they've engaged in. It's true they are not true monopolies, but they exert exactly the problematic behavior of a true monopoly. It's very unlikely that the free market would ever fix this.