But the problem right now is the opposite. The problem is that we MAKING them live in the countryside instead of allowing those that want to to live in the city.

Let's very much make it so living in the city is just as cheap as living in the countryside. That way everyone can decide for themselves which life is better, instead of being forced to live in the countryside, because the city is unaffordable.

Most of the jobs are in the cities already, even without the hypothetical scenario. Most developed nations are mostly service sector, and demand for services is mostly where the people are, despite remote working being possible in some cases.

(Does anyone call for new primary industry jobs these days, or is that basically robots first now, with the jobs being mostly service and some manufacturing?)