I'm no economist but here is how I think of it. In an ideal world let's assume every worker is replaced by one AI / robot that is an exact clone of them. Then let's say there is an ideal government that taxes all the income each person's clone makes and hands it directly to them. In such an economy nothing would change, things would go on as they always have.

Now some will be unlucky and end up with a clone that makes them way less than average. So to fix this the salaries of all the clones are put into one pot and redistributed as "UBI". Given the wealth disparity, most people would end up better off than before, the high earners of the past will be a bit worse off though.

But of course we are not in a perfect world, in reality there are many inefficiencies, and no company would accept a 100% AI worker tax. However, these AIs are presumably not just our clones, but 100x better. So we are in a position of abundance not scarcity. There's enough eggs for everyone. It becomes a question of distribution and policy