I've been a manager for 25 years, and the reason it pays so well is because managing humans is necessary yet miserable work. Even if I received a minimum income the world would still need managers, and that would mean me, and my work would still be miserable.
UBI is a flawed economic concept meant to bolster the poor. So why don't we just do that? Targeted UBI, to help teenagers and new mothers, is a worthy goal. UBI needs to target key roles like this that help society rather than some concept of ending work.