Well thought out post .... so are you of the opinion that machines / AI will be the source of artificial 'food' created with optimum nourishments etc. ? Or will good old agriculture be required ... planting, feeding, harvesting all to be done by robotics? What of pesticides, pests, the good old bee?
For me the idea is too far fetched, although I am fully onboard that automation and AI will continue to grow in the future and play an important role but more in 'lifestyle' technologies like VR, Metaverses and medical procedures. That what you envisage is more something that should be pursued by Elon Musk for his Mars settlement.
As regards UBI I think that is a dystopian poorly thought out construct and will never work. The Divided States of America is a perfect example of this. There are millions of Americans who do not want to go back to work because they are receiving more from the State than they would from their employer...
Human basic truth.... the majority of the population 'if their is no incentive to produce..they will not produce.
Ai and food: Most definitely in the future, we will produce food in a factory, from greens to meat. For the meat, we dont need to farm animals, meat will be grown in the factory, without brains and a body connected to it. Some success already in this area. They take some cells from an animal, bring them to the factory, apply s process to get it growing fast. For now, the growth is slow, something like 6 months (if I remember correctly) for the size of a chicken. To become cost-effective, the growth needs to be faster. Give it a few years? Greens: We gonna build vertical farms for starters. Farms that can live on the open sea (no forrest need to be sacrificed anymore), robots will do whatever needs to be done, 100% sure. No humans are required anymore.
UBI: incentive to work... I know (you wrote this) you don't believe in AI/Robots doing everything for us at one point in time. When that is gonna be the case, and plenty of humans need to work to get things done the way we want, then most likely something like UBI may not be required. However, such a future may seem the most likely in your view. Recently our taskmaster hive user posted about the decrease of jobs, which he used to tell the reader with hard figures; These figures show a global decrease in the number of jobs. AI/Robotica will make huge steps coming few decades. I wouldn't be surprised if in let's say western world countries in let's say 2 decades, just 10% of the current amount of jobs are needed. All the rest of the tasks will then be carried out by robots. This will give an income from a job for just a few in our societies. How will the remaining majority get to their income to pay for at least their basic necessities? If you don't believe in such a scenario, try to think about this still under the 360-degree method in which all scenario's how unlikely they seem, are covered in our thinking.
EDIT:
Some interesting results with UBI tests in Finland: https://www.mckinsey.com/industries/public-and-social-sector/our-insights/an-experiment-to-inform-universal-basic-income