Right now in the United States, 95%+ of people get their basic necessities covered, one way or another. The additional goods produced and services utilized will only require a "relatively" small reallocation of capital resources to their production.
The way I conceptualize UBI is partially an accounting trick, since a large portion of the revenues and outlays would be just changing money that people currently spend directly on goods and services to money that first gets taxed and then goes straight back to people who then spend it on the same goods and services. It's partially changing the incidence of social costs--hospitals that once had to eat the costs of the required treatment of poor people would then not be punished, and instead (depending on how the funding taxes are structured) the holders of income/wealth in society would eat those costs. Some of it is renaming existing programs and more efficiently administrating them (instead of food stamps with complicated bureaucracies, people just get a check). And for the few people actually starving or freezing to death because of lack of funds in the USA, yes, that's genuinely a new cost we'd have to bear, but that's a rarity and I don't feel too bad about new taxes if it's genuinely saving lives.
There are second order incentive effects in both directions that are certainly worthy of consideration, but a naive consideration of the facts on the ground suggests it's not at all impossible or even requiring any real magic, given the political will.