Could you explain why? If you offer UBI for people who move into a new town, why shouldn't a huge number of people from all over the world take that offer?
This assumes that UBI communities don't create value.
But the city is not for free. UBI is just enough to pay for a basic life. If you want to eat great food, have a nice house or want to impress your friends or send your kids to a good school, money is needed. Money, that comes from taxable activities.
The advantage of UBI is that there are no homeless people, no beggars, no petty crimes, no robberies. There is no excuse for robbing somebody because it clearly is a move to get luxuries. Punishment can be harsh, including expulsion from the city.
Thus you have a friendly city where people can create value the most efficient way.
All the people who don't create taxable value still create value. They create the network effect of the city and they manage the focus of the production processes. Somebody has to be an early adopter of a new restaurant or a new service. Who is better suited than somebody who has an entire day to spend?
After all, money that is spent in the city is not lost. The only problem is spending money on external goods which can be managed by taxing imports.
> The only problem is spending money on external goods which can be managed by taxing imports.
But you need the import (of money, specifically) to run the city for the people who live there on UBI. I don't believe that UBI will ever be self-sustaining, but I'd love to see an experiment that tries to prove me wrong. For now, they're all like "free energy machines" that are plugged into a wall socket: outside funding paying for the UBI. But that doesn't help, because you need self-sustainability, or you'll need an external work-force slaving away for your luxury not to work. And I'm pretty sure that external work-force won't be too happy about that.
Why would you have to import money? You can have your own currency within the city. You only need external money for external goods and services.
The premise of UBI is that it creates a more productive society. If there is no possibility to be self-sustained, why implement it? However, if there is the possibility, then funding is possible because you can sell future surpluses for external current currencies and get the city going.
As far as I know, there have been ancient UBI societies, like Persia and Egypt where everybody received free grain.
Don't forget that luxury is the tool of kings to show their power. On one hand, kings live in luxury, but they still keep working. On the other hand, not working stops being a status symbol and a luxury if common people do it by default in a UBI society.
UBI is like heat pumps: you don't use the energy of the wall socket to create heat or cold, but you use it to move energy from one area to another. That way, you create a net surplus. With UBI, people stop worrying. All that mental energy is used to create value. The insight needed for a UBI city is the ability to tax it.