OK first off, the USSR never had a universal basic income. They were just a tyrannical regime who devoted the government toward giving asspats to their buddies in the inner circle. They were the Republican Party, calling themselves communist. Every time a UBI has actually been implemented, it's worked great, with not one single kulak sent to the gulag.
Secondly, currency does not work that way. The government just prints money. It doesn't spend taxes. Tax dollars are effectively just money burned, in order to limit inflation. So no, there's no risk of being "unable" to pay a UBI. The only consideration should be how much money to print in order to maximize quality of life for the country. Anyone expecting to be paid back at the expense of that is delusional.
So a UBI would not make it where the poor cannot eat properly. It would just switch the dynamic so sellers have to react to increased wages, rather than wage increases reacting (with a delay) behind price hikes by sellers. That delay is stolen money, and a UBI would end that theft.
Personally I think that it's ridiculous to make it so the criteria for "who starves to death" is how much money you have. So food shouldn't cost money. We can figure out other ways to decide who gets the food produced.
But if you must sell food, for money, then a UBI has (in every case) been shown to improve things overall. It's the difference between a billionaire having "literally infinity times" the buying power of someone with no income, to "only a billion times" the buying power. Poor people might see prices rise, but they already have $0 to pay for anything, so it doesn't matter how high or low the price is.
