My bad for the lack of reading before replying

They will be locked up against their will, unfortunately (until a future society figures out something better)

They don't need to be forced to stamp license plates under socialism (prison abolition can't happen under capitalism ofc), but if work were available to them they could receive a fair wage. That would not be slavery, it would be imprisonment, i guess (did I contradict my original point? Idk Maybe, but I still see it as fundamentally different than how a "prison" is defined in the 2020s).

Also "prison abolition" doesn't need to be literal, it's just a goal to work towards over many generations. Is it even viable? Who knows, but it's not gonna get figured out during our lifetimes anyway. In the meantime, we can start to restructure our society in a way that will minimize the scale of prisons, and maybe our grandchildren will find a way to phase them out totally, but that's their problem.