Universal Basic Income Refusing To Go Away

Thomas Paine supported it, Napoleon considered it, Richard Nixon tried to make it law, Martin Luther King Jr advocated introducing it and Elon Musk thinks it is inevitable and it seems to
become a Left Wing cause and while i am generally in favour with anything that side advocate, i just can't seem to get behind the idea of a Universal Basic Income which is an idea which refuses to go away.
Two area of Britain have now been picked to receive £1,600 a month for two years on the condition that they can be observed to understand the effects on their lives.    
Universal Basic Income is an old idea that is gaining momentum, especially amongst those with a left-wing ideology now that Ai is threatening to reduce the opportunities for paid employment for all and while i can see plenty of benefits, moistly reducing poverty and inequality, i always ask, and never really get answer to, how is to going to be paid for?
To pay every one of the UK's 33 million working citizens £19,200 a year would cost £633 billion while the UK's current tax intake is £786 billion, an amount which would reduce if you handed them £19k a year and some stopped working or reduced their working hours so less tax paid.
In 2018, Finland held a two-year basic income experiment, paying €560 per month to 2,000 randomly selected working-age people and found that recipients were happier and healthier but decided to not proceed with expanding it and i can't see anyone else rushing to give it a go either.
Amazingly, there are some on the right side of the ideological fence who deem it worthy of having a look at although for very different reasons to the left, they see it as a way to dismantle the welfare state and reduce Government bureaucracy
Some say that looking farther down the road, the threat of technological unemployment will mean that Universal Basic Income is inevitable and The World Economic Forum predicts increased automation by 2025 will mean 43% of businesses reducing their workforce but until someone explains to me
how it won't be ruinously expensive to a nation, i can't support it whatsoever.