If money becomes "free" it will become worthless. And there isn't enough wealth of all the billionaires in the world, to fund UBI.
This betrays some really entry-level thinking about money, where you're believing what it says on the back of the software box. (Remember those?) The idea of trickle down economics was that the wealthy were supposed to spend and/or invest their money so that it went back into circulation. That's what happens when normal people get it. It gets spent about five times before it winds up in some rich person's pocket. When rich people get money, it only gets spent twice or so before they put it someplace where it's not employing anyone. They've got it in some kind of tax dodge like in some kind of account held by a trust their name isn't on (legal in at least four states) or just stuck into some kind of investment they can devalue intentionally. They used to use art for this, but that tax loophole has been tightened, so they have to use cars and whatnot again.
The idea that isn't enough money to take away from the billionaires is inherently falling for trickle down economics. It's buying the idea that they are the job creators, when they are the job murderers. They choke the air right out the system. When we get the money, we spend it.
We are the job creators.
Yes, AI can be scary. But like all other past automations, it isn't going to end civilization as we know it.
We separate history into ages and eras in retrospect for convenience, but we do it along borders which measure real and tangible effects which affected real people's actual lives. These people are not imaginary because they are past. Their challenges were real. Industrialization built empires and killed people, sometimes directly and in numbers. It changed the way we did everything. In a very real way, it ended civilization as we know it.
The information age represents a paradigm shift as profound as the industrial revolution. A huge number of workers get paid simply for causing practical and desirable shifts in the contents of storage devices. Many of them are doing work which is frankly redundant or worse, which will be actively discarded. How are they getting paid without the whole system collapsing? They're not contributing anything to the actual function of society whatsoever, but many of them are receiving good salaries. In fact, they are putting load on the HVAC and burning fuel commuting and so on, they're a net negative in multiple ways. Why not pay them less to stay home? Then when the money you gave them gets spent five times before it trickles up to the wealthy, it will have done a bunch of work in the process instead of getting parked in a blind perpetual trust in South Dakota.