This is only a fundamental problem if UBI is so high there is no incentive to work whatsoever. Every UBI proposal I've seen puts the income level at, or some sm

This is only a fundamental problem if UBI is so high there is no incentive to work whatsoever. Every UBI proposal I've seen puts the income level at, or some small fraction above, the poverty line. The majority of adults (currently) earning more than that are unlikely to want to lower their standards of living. Some will, sure, but not most. And likewise many of those in poverty would be willing to work to raise their standing of living beyond UBI, especially if they have more of an economic cushion to find a better position. So I don't think we need worry about everyone stopping working. What we need to consider is the marginal effect of the small population that does. If the unemployment rates doubles, what impact would that have on the economy? There is a lot to figure out with a problem like that, but it is a different caliber of problem from total economic meltdown.