You are confusing "federal taxes" with "federal income taxes" and assuming the only way to increase the latter is to multiply the existing marginal rates without changing the structure; since a one portion of the drive for UBI is to address concentration of returns in high-end income and capital gains, the natural first thing to do is to uncap payroll/self-employment taxes and tax capital income the same as labor income (both the taxes on labor income styled as "income tax" and those styled as "payroll tax". That -- alone -- more than doubles taxes on long-term capital gains.)

There's also other income that excluded from taxation or taxed favorably that is concentrated at the high-end that could be targetted.

This whole theory hinges on automation taking a significant bite out of the workforce, which will raise profits in direct proportion to lower costs. If companies aren't paying their employees anymore, a portion of their proceeds should go to paying back society as a whole - after all, if there's nobody to buy their product then they are dead as a company.