[mcguire]

You are correct; the money supply isn't an issue. However, inflation within a localized area of the economy is a thing (e.g. housing prices, health care).

UBI is a transfer of money from the wealthy, who would have used it to buy filet mignon or something, to the poor, who would likely use it to buy food and shelter. One should expect the prices of food and shelter to rise, relative to other products.

[idontpost]

And? That's not an argument against UBI. These things have equilibria and rising prices push up supply. The fact that prices may (I emphasize may, because there are other factors at play here that you conveniently ignore) rise doesn't change the utility of raising the floor on standard of living.

I already live a better, more comfortable life than any Roman emperor ever did. We have the means to ensure that no one in our society suffers in destitution, by a vast margin, and that margin increases continuously as automation of menial work proceeds over time.

Not doing so because it might not be "optimally efficient" according to some arbitrary metric is inhuman.