UBI would never work. It ignores basics of how humans operate. We have it in some sense in France. The problems it tries to address are only amplified after UBI.
Do you mean RSA[1]? My french is quite bad, but as I understand it, the RSA is tied closely to employment and has complicated work obligation and subsidizes employers for keeping employees at low hours. RSA appears to be extensively means tested as well (which UBI is not supposed to be).
There are numerous independent social programs in France. RSA is one. People could receive input from up to 3-4 social programs.
Consider CDI contracts at universities. It has become a sort of UBI. People show up once every few weeks. Never publish papers; never teach properly; never go to any conference; etc. Totally detached from academic life. And they can't be fired. You know what they do with the UBI?
-- Become members of unions. Unions were supposed to protect workers in 80s. Now the least productive members of the institutions join unions to protect themselves. They kill reform policies and maintain status quo.
-- Work is associated dignity. You can't have two classes: workers and suckers. So UBI recipients, holding into administrative roles and unable to do meaningful work, try to fail non-UBI takers.
-- Fail those who actually do their jobs. Otherwise, the gap is going to be problematic.
At the end of the day, UBI would only shift the baseline. The same problems it tries to address exist after the administration of UBI.
You would be surprised if I go over details. America's left does not understand what it's getting into. France's system has really been an eye opening experience for me. I highly recommend people spending time in Europe.
That sounds more like a jobs guarantee than a UBI. Many UBI proponents are against a jobs guarantee for fear of these kinds of outcomes.
UBI is untethered to any conditions on people. So there are no bad incentives created by the system (no good ones created either, of course) nor is anyone part of some group that they try to homogenize into something unproductive.
[1] https://fr.wikipedia.org/wiki/Revenu_de_solidarité_activ