I think you accurately characterize a fringe of HN, but I think support for UBI, etc., isn't all (or even mostly) about imminent AI singularity (though certainly some is based in that belief), much of it is a belief that the Band-Aid over traditional capitalist economic relations provided by the modern mixed economy, particularly as implemented in the US, which remains heavily based on the assumption of steady wage labor with one primary employer (which, itself, is almost a pre-capitalist, feudal/manorial model) as the normal means for people to earn income, is fraying given present levels of automation and preferences for ad hoc interactions, necessitating a more efficient model of support to cushion the blows of long-term and short-term dislocation in an increasingly automated and increasingly fluid market, a need which will only get more acute with increasing automation (even fairly mundane automation that falls well short of AGI.)