I think there’s a strong bias towards hacking and cool side projects from the hackernews crowd. But I’m not so sure much of the general population would use their free time afforded by UBI for productive and useful endeavors. At least from my observations there’s a significant portion of the population that uses their free time to be idle and veg in front of the TV and/or get wasted. My concern with UBI, even if it was financially tenable as it would underwrite a whole lot of that - including the more criminal, antisocial sub-population.
Wouldn't convincing the criminal part of the population to just stay home be a net win? Policing and prisons are both notably more expensive then welfare.