I really think it makes sense to start with a ludicrously inadequate basic income guarantee / social dividend and scale it up gradually over time, rather than waiting until some day when society decides it can suddenly afford to pay everyone $40k per year.
make it a dollar a day! test the infrastructure! run it for a few years and tweak the system and taxation levels! then gradually ramp it up over time.
even a dollar a day is giving homeless people seven bucks a week they wouldn’t have otherwise seen