Name a permanent large scale universal basic income (UBI) programme that is working today right now and is economically sustainable to a country supporting tens of millions and to hundreds of millions of people paid a basic liveable income.
No short-term experiments or one-off payments supporting less than 1 million. An actual UBI programme in place.
Use all those chatbots and search engines you want and you'll see why no examples exist and it is simply dismissed as a failed utopian idea.