UBI itself isn't usually considered taxable income in the proposals, so effectively that's what happens.
Personally, I wouldn't increase pre-UBI marginal tax rates for taxable incomes below (pre-UBI median minus UBI), but I'm not a right-wing UBI proponent, and I favor focusing first on taxing capital income equally to labor income as a revenue source.
Personally, I wouldn't increase pre-UBI marginal tax rates for taxable incomes below (pre-UBI median minus UBI), but I'm not a right-wing UBI proponent, and I favor focusing first on taxing capital income equally to labor income as a revenue source.