I don't know enough about UBI to say anything for sure. I know that either UBI will have to be so slow that it'll be useless for those in a first world country

I don't know enough about UBI to say anything for sure. I know that either UBI will have to be so slow that it'll be useless for those in a first world country (like 250 dollars a year) or else we'll have to have far stricter immigration controls than ever - a UBI for first world standards would be unimaginable luxury for those living in third world conditions. Fundamentally I think it comes down to population control. A geometrically increasing population is simply not sustainable for any long enough period of time. My personal opinion is that if UBI could be linked to contraception (you only receive UBI if you're not allowed to have children while on UBI or take care of children with your UBI funds) then that could work.