As for issuing the tokens, there are a variety of UBI systems that handle that without a centralized authority. CirclesUBI and Idena come to mind. Admittedly some work is needed here, but the technical barriers are not the hard part.
The hard part is establishing the collective political will to build a culture around accepting them, otherwise it's just meaningless numbers.
And you'd want it as an alternative for cases where the other money is questionably legitimate. Like if the people who control its supply have stopped acting in the best interest of the people who use it.
So I agree, universal solves the problem, but you're not going to get universal from a bureaucracy. You've got to bake it into the design, similar to how backed-by-gold is baked into the design of the money we're currently using. It needs to be legitimate because it's universal, rather than being legitimate because you got it from somebody who has a lot of guns and has promised to behave themselves.
I'm very pro-UBI, I just don't think that saying pretty please to the government is the way to get it.
Where do you get that idea from? The Federal reserve flatly denies it: https://www.federalreserve.gov/faqs/currency_12770.htm
The US came off the gold standard in 1933. I'm pretty sure no country uses it now.
It's a system that works, more or less, I just think it would work better if it had some alternatives to compete against. Alternatives would give the powerful a reason to care about non-monetary outcomes.
The whole thing has aggregate behavior, and we're going to be better off if we develop a way to shape that behavior independently of how we deal with individual bureaucrats.
If somebody offers you money that was issued by an organization that has been bombing your neighborhood or poisoning your water you should be able to reject it and still have other options, because to accept it is to contribute to the continued economic power of your enemy such that they can keep harming you. That's independent of whether you're in a position to have the relevant politicians fired.