You're right, I'm thinking of GMI - Guaranteed Minimum Income - as I've seen the two spoken of interchangeably while that doesn't seem to be the case.

My fear when comparing the two would be that UBI would, over an extended period of time, put us right back where we started. I say this because UBI would essentially just be moving the starting point, $0/mo in this case, to say $2,000/mo, and that markets would eventually catch up to this resulting in hyper-inflation, i/e $25 gallons of milk.

However, since as wikipedia says, "most modern countries have some form of GMI", either I'm being too optimistic about GMI or too pessimistic about UBI. Then again, perhaps the issue evolves into one on taxation, loopholes, etc. since GMI exists and we're still discussing how to "fix" this issue.

https://en.wikipedia.org/wiki/Guaranteed_minimum_income

Yes it's basically a credit.

I think all non-business deductions should go away and turn them into fixed credits (vanishing most of them entirely). Right now two homeowners each with $1000 in deductible mortgage interest, have different tax liability reductions if they're at different tax brackets. The one in the higher bracket actually ends up with a greater reduction in tax for the same deduction. And so on.

As you define it.

I define UBI as having a floor on people's income, where the government ensures everyone is above that floor. So it's universally ensuring everyone had a basic income.