"I must study politics and war that my sons may have liberty to study mathematics and philosophy. My sons ought to study mathematics and philosophy, geography, natural history, naval architecture, navigation, commerce, and agriculture, in order to give their children a right to study painting, poetry, music, architecture, statuary, tapestry, and porcelain."

> My fear is that true UBI will create a giant section of the population whose sole purpose is to consume food/water/utilities and create meaningless art, music, babies, etc. which raises questions about what our purpose in the universe is.

What they consume is culture, culture has a price tag, and the most sought-after culture is the most expensive.[1]

I'm sure UBI will change marginal spending behaviors. The question is by how much. I doubt it would change spending habits so much that civilization collapses, but even if it would some evidence of that effect would be captured by studies attempting to capture more boring marginal effects.

[1] Including the culture of non-consumerism, which uncoincidentally is conspicuously favored by the elite and wealthy.