"Enact" implies the government restricting everyone to working 20 hours per week. That's a violation of our freedom to work as many hours as we want.
I do support you in that all of people shouldn't have to work in order to meet the basic needs of life today (food, housing, and connectivity). Agricultural and industrial efficiency and automization has advanced to a point where we can provide these basic needs to 90% of the populace with only 10% of people maintaining/operating these machines.
A lot of people will continue to work 50 or 60 hours, because a lot of humans are naturally inclined to work. They derive pleasure and satisfaction from it. I would myself personally continue working, perhaps even harder than I do now, but would direct my efforts towards things that I enjoy more, and that are potentially more impactful, meaningful, and beneficial to society. Ensuring that everyone's basic needs are met would give people great personal freedom to pursue what they want.
How would we implement this? One possible way is basic income -- although it might be beneficial to incentivize productive and meaningful use of freedom that basic income gives people. We don't want a country where 50% of the population spends time watching soap operas, and eating junk food.
Just some of my thoughts...