Based in your first two sentences, I think your understanding of UBI is mistaken. You seem to be under the impression that people don't or can't have a job when there is UBI. This is not the case. If you don't believe me, just look at Alaska.

Everyone enjoys some sort of benefit, tax break, subsidy, etc. from the government. UBI is the same thing in the form of a regular, universal transfer payment. Nothing more, nothing less.