The planet I’m going to is Deisos, covered 97% in water, the only landmasses being countless archipelagos of small islands. The inhabitants left the UPMW because they decided to lead a carefree life void of things like government and money.
By choosing to live on the planet, you have to contribute to your local community in some way: fishing for food (and the fish are massive), building houses, etc. Whatever it is you do, you do for free. In exchange, you’re given things such as food and housing for free. The society there is the subject of many studies and textbooks on sociology and political science.
Luckily for Deisos, its small number of inhabitants are all dedicated to living a simple and carefree life, so there seems to be no fear of greed or corruption. Even with their jobs, they spend most of their time just enjoying the islands and the ocean.
They do have some small use of currency. The only visitors allowed are those who are considering living there. You must pay a fee, and you get to live there for one month as a trial. If you choose to stay, you become a permanent inhabitant. This fee is used to import some things from the outside galaxy that simply can’t be produced on the planet due to its lack of industrialization and mining, like medical equipment.
Besides the committees that handle fees, immigration, and shipments, the only other governmental entities there are very small volunteer “police” forces. Very little occurs there that a justice system is needed for, but occasionally it handles disputes. If anyone were to rebuke me for being there, it would be them, but I don’t know what they would actually do to me. They don’t have any formal legal system, and as far as I know they don’t even have weapons.
Looking at a map of the planet, there are several dozen of these loosely defined communities which are usually spread across an archipelago. Some inhabitants even choose to take the idea to the extreme and go live on an island separate from any community.