[gojomo]

Good point; after posting I wished I'd said "...cash welfare", because of course in-kind transfers of goods and services would be immune to any amount of inflation.

Indexing the UBI amount to some basket-of-subsistence-consumption could likely address this concern.

(The handling of existing-conditions is a regulatory issue orthogonal from UBI. I'd prefer a UBI replace all "income-supporting" programs – including things like food stamps and housing vouchers – and also obviate many rules premised on the idea that the threat-of-privation captures people in bad jobs/relationships. But "structure-of-market" or "acceptable offerings" or "required minimum standards" regulations are a separate matter.)