Monopolies are the opposite of free markets. Even pseudo-monopolies are counter to free markets as they inevitably use their dominance to manipulate the markets in their favor.

That said, I feel like there are a lot of libertarians who feel like free markets are core to the philosophy, and about as many who believe that free markets are a nice-to-have, secondary to everyone doing whatever they want in the market regardless of its impacts.

I don’t think it has to be like that. But I would distinguish between two categories. Limitless resources and fixed ones. The earth is constantly supplied with light energy from the sun and the earth’s heat is also a virtually inexhaustible source of energy. The same applies to the creation, processing and transmission of information. Anyone with the right equipment can produce these resources themselves, because they are available in almost unlimited quantities. In these cases, everyone should be able to buy the equipment and sell the products on the free market. The transport costs and the necessary infrastructure could be financed directly through transaction fees. Sewage treatment plants or waste collection points could also fit this bill. Any waste produced by a household that cannot be recycled (compost, reuse, economical use of resources) must be disposed of by a company on the open market at a reasonable cost.

Water, fresh air, good land or other finite resources are different. They cannot simply be generated and are even more dependent on location. In my opinion, this makes it very complicated who is entitled to these resources. Take, for example, an owner who owns part of a river on his property. He could of course pump out all the water and sell it on, but he doesn’t own the whole river, so every owner of a river property above could do the same. Taken ad absurudm, every owner of a spring could then claim his water for himself and every owner of a property could claim the rain on his property, heck, every owner of a beach by the sea could claim that the water also belongs to his property and start pumping it out. For distribution, on the other hand, one could fall back on a decentralised p2p network as above, where the resource is bought on the free market and the transaction costs cover the maintenance of the distribution infrastructure.

I don’t know of any monopoly that wasn’t created through coercion

While technological innovation to disrupt or supplement these “practical” monopolies are welcome, I do think they have a place.

Clues to achieving sustainable and “democratic” management of such infrastructure are, IMO, to be found in the various explorations of municipalism, Elinor Ostrom’s “commons” studies, and Henry George style ongoing community compensation for monopolized inelastic resources.