This seems like a strange question to ask. I don’t encounter many libertarians who support UBI, nor UBI proponents who claim to be libertarian, so I’m not sure

This seems like a strange question to ask. I don’t encounter many libertarians who support UBI, nor UBI proponents who claim to be libertarian, so I’m not sure that the people who advocate UBI would agree at all with the beliefs you listed. As for me personally, I’m open to the idea of basic income, but I specifically like Milton Friedman’s “Negative Income Tax” idea more. As for why, I think that (1) we can afford and have shown politically for several generations that we do want a basic social safety net for everyone, and (2) the current way we provide it is pretty mediocre. The idea of replacing the current system with simple cash payments seems to me like a potential cost saving and efficacy improving move. But since it hasn’t been done on a large scale before I’d rather see that idea thoroughly tested and researched before I’d have confidence that any nation should fully adopt it, and IMO its not very easy to design a good test. Thus I’d say those ideas are more of an intellectual curiosity than a position I’d advocate.