Trying to maximize earnings is basic human behavior, sorry to break it to you. Welfare scams occur regularly, and that's before UBI.

And you're dodging the bigger question: I'm on UBI and my money runs out, can't afford to feed the kids. Multiply that by at least several thousand people every month. Now what?

How can maximising earnings be basic human behaviour when 'earnings' have only existed for a few thousand years, a tiny fraction of the history of our species?

Food banks exist already, why would UBI change that.

Same as now. You don't get more food stamps just because you ran out.

The difference is it's earmarked money today. There's no potential to spend your food money on a phone and then claim you can't buy food at the end of the month.

Most countries just give cash to people without income, they don't bother with a separate food program. That seems to work fine.