Nope. UBI is
universal. Even Bill Gates would get UBI.
Not only are you wrong (or at least not justified) in your assumption that most people would stop working (
https://www.nber.org/system/files/working_papers/w24312/w24312.pdf), you also haven't taken into account that people want more than having their basic needs met. People will most likely not stop working.
But you are right in the assumption that people will stop working in jobs that are underpaid, dangerous, or for other reasons not likely to be picked without need.
There will be slackers, there will be people who reduce their workload, there will be people who will become self-employed, working only on things they like or when they want to make a big purchase, but most people won't change their lives at all.
Who will have to change are employers, because it will be easier to walk out of a toxic work environment.