But in the long run people are not going to just sit around collecting UBI. They can still work, but on other things. Society will develop new areas of interest in which it will invest the available money. The focus will fall on science, sports, culture and social projects, which are going to keep everyone busy and at the same time advance us even further.
As society changes, education will have to adapt to the new requirements. There will still be jobs, but in domains that perhaps now are not even imagined.