I feel like a bunch of things must be being glossed over. Let's say UBI happens. How will people in NYC, SF, Singapore, London, and other high priced cities afford rent? Those are also the type of places where the jobs are. Not all jobs can be work from home.
UBI might let you live in some small town in the middle of nowhere where the rent is low but it's unlikely to let you live in a high demand area. You could say "rent control" but that's not a solution. All that does is start a lottery of who gets it live in the city and who doesn't.
Further, there's a ton of jobs that need to be done but arguably no one wants. jobs like farming and shipping, stocking grocery stores, construction. Ok, so UBI lets everyone quit and now those jobs have to pay more to get anyone to take them. But then all the costs go up and UBI is no longer enough to make it. Raise the UBI and you get a vicious circle.
I don't know all the reasons prices are out of control in the bay area but for example, I ordered 3 simple Thai dishes the other night. $135! In Thailand that would have been $6. 3 burritos in the poor part of town, $60. 4 plates of Chinese dumplings, $80. My guess is this is in part, high rents, and paying higher wages. Sounds great, but now no low-income people can afford to eat out.
UBI would take that even further because (see previous paragraph)
Someone will now chime in how it's bad to make people work in jobs they don't want. I don't disagree. My point isn't that people should work shitty jobs. My point is UBI won't fix the problem.