Well, first, extracting any value whatever from a kleptocratic State system isn't very likely, i.e. they'll never agree to pay people a UBI.

Second, if they did, it would lose its value because the payment, made in unearned fiat currency, has zero comparative value to staples of human sustenance. Only a fool would keep on working to earn that same currency as could be acquired without work. The AI system wouldn't be able to sustain itself on currency that has no value proposition, so it would decouple itself and its products from the UBI currency too.

Essentially, even if computers could provide all of our needs for life, UBI would make that task not mutually beneficial by removing our need to maintain their requirements. No human could benefit from working to take payment in a UBI currency either, because there would be no products to exchange it for.

Currently, currency can be thought of as representing some labor, but more accurately as a store of value related to labor because some forms of labor are more lucrative than others. With UBI, that would no longer be the case. The UBI currency represents nothing in particular, and has no method by which to preserve its own value over time.