All those things are fixable by using curves instead of hard thresholding points. A largely USA specific set of incentives problems isn't a general argument for

All those things are fixable by using curves instead of hard thresholding points. A largely USA specific set of incentives problems isn't a general argument for UBI, which claims to be a global solution. I think there's also a problem with arguing the solution to badly designed welfare systems is a far bigger one. What makes you think it'd be run better? As I point out elsewhere, UBI will still be means tested and still require administration, if only to restrict it to residency in a local jurisdiction.