Normies / statists believe that when AI takes most jobs, UBI will save them.
I think there is a potential problem with that: it sees government as something we have, because we want it. It comes from a belief in democracy. The naive belief that we the people have created a government, so it can serve us.
The reality may be much less bright for them: government is a business and as such, it's subject to economic incentives.
If you're not useful to the market, you may not be useful to coercive authority either.
It's not obvious, because people have traditionally been useful. We tend to only look at history, and we don't have a history of human uselessness to go by.
Government can be viewed as a farming business. The politicians in power are farmers and their job is to look after their livestock to maximize the harvest (milk, fleece, what have you). The livestock is kept on life support, because what it produces is worth the cost. And it's worth the cost, because it's essentially slave labour.
But when machines replace humans, farming people will no longer be economically justifiable and the business model will die.
The state won't get defunded or destroyed; it will simply be abandoned.