As a side note, why are you worried more about the rich than the poor?

I am not. I’m offering the argument that a UBI may well lead to a less productive population, which makes it even harder to maintain a UBI in the first place.

They will get UBI too so worst case they hit the same floor as everyone else.

But if there are no longer rich people to be taxed because they have been sucked dry then there is no source to fund the UBI. Hence the notion that “rich people will fund the UBI” doesn’t fly. Not to mention that wealthy people find it relatively easy to move to other countries with less taxes.