The other innovation of cryptocurrencies is bootstrapping 'value' for scarce digital tokens; in this sense, UBI based on a cryptocurrency can be self-funding.
That only works because of investment and speculation. You would specifically not want that for UBI IMO, because speculation could crash your currency leaving people that rely on it unable to purchase anything with it. I'm pretty sure you would need to tie it to a stable real world currency for it to function for its intended purpose as a basic income.
