I though slavery was having a job you couldn't quit and weren't paid for? Having no job and guaranteed income seems pretty far from being owned by another human.
If dependence on a government for basic necessities is slavery, isn't any form of dependence slavery? Are trust fund recipients slaves? Are workers who depend on an employer slaves? Are people in debt slaves to their creditors?
Workers depending on their employers are wage slaves. It is particularly bad when in countries like America, a worker's _health_ is dependent on their employer.
But in general being "dependent" on the government is 100x better than being dependent on individual employers. I'd be much happier making 30% of what I do now if I did not have to plan for existing 30 years down the line when I'm automated, found non-essential, a victim of ageism, or simply invested in the wrong skills.