A thought experiment...
If some rich benefactor, say a mysterious person with truly unlimited resources, were to decide to be the provider of UBI for every citizen of a country. Everyone suddenly has an additional $500 each month to do with what they wish, spend, invest, save or some combination of the three. The only proviso is that the extra $500 is not taxable in any way (so the government does not get a tax take from the UBI). How would that impact the economy of that country?
(Remember this is a thought experiment so you can't question how its possible that any of its premises are possible. It is what it is, and we simply make it happen)
Of course it would massively boost the economy? To deny this is to deny logic. Does anyone disagree?