The problem is that UBI is in conflict with arithmetics. Short of near-total redistribution, it's impossible to provide a decent level of UBI for everyone. Total redistribution doesn't work, because economy needs markers as ways of price / demand discovery, and markets apparently lead to power-law distribution, not flat.
IMHO, the realistic option is a thick enough safety net for those who is going through a rough spot, for the disabled, etc, via both taxes and charity. But the vast majority will have to work, in one way or another, until machines completely take over, like in the Culture books by Ian Banks.