The argument for UBI is that society is going to write off the bottom half of the population anyway, so something is better than nothing.
Trump's populist promises to keep the coal mines open and auto factories rolling and dial the American economy back to the 1950s won't work, the world has moved on. Reeducation and retraining won't work at scale, especially not in the US where education means an unpayable private debt in many cases.
So if not UBI, then what?