This does not address the relative purchasing power change on the left of the bell curve.

The whole purpose of UBI is to increase the relative purchasing power on the left of the bell curve.

But inflation (sum total) is a moot point if total supply of dollars for total demand stays the same. Prices might temporarily increase for staples, such as shelter and food, but that should incentivize sellers in the economy to supply more staples, and fewer luxury goods.

The additional supply will eventually bring prices down, but end result is more people have more of the basics.