Apart from needing those technologies to exist before being able to claim them as reasons there won't be a labor shortage with UBI this is still completely independent of rich people existing today without causing a labor shortage. Perhaps it's a funding source to prove out things like automation by redistributing said wealth but the existence of said wealth in the hands of a few is not prove lack of labor in all is sustainable. To do that you must actually prove the alternative means of production out - regardless if the wealthy exist.
The problem is that we are dependent on these zero sum games to regulate our economy and as a result these zero sum games end up consuming all our our productivity gains and making up a progressively larger share of the economy.
The goal of society should be to become post-scarcity. All of our technological progress has led in that direction. We currently just live in a period where the majority of the gains have been captured by very few people and that has allowed them to exploit human labor to enrich themselves vs. building a self-sustainable society. Engineered or not, I think that's the inevitable end game of continuing humanity.