And the answer is that prices will probably be expected to go up to some degree as a one-time thing, in a way that would be approximately a wash for those already with plenty of income, but where it still makes a huge difference for those with little/no income, which is precisely the point.
For example if it's a one-time inflation bump of 10% and UBI of $10K/yr., then:
Person A with income $100,000/yr, now makes $110,000/yr., worth $100,000 in previous dollars
Person B with income $10,000/yr, now makes $20,000/yr., worth $18,182 in previous dollars
Person C with income $0/yr, now makes $10,000/yr., worth $9,091 in previous dollars
And it's important to realize that the inflation is a one-time event. Prices will rise but then they'll stop rising. And if it were 10% inflation over a year, that's the same as the usual targeted 2% inflation rate but compressed from 5 years. (And the central bank might very well target 0% inflation over the following 4 years to compensate.)
What's the basis of that? The UBI is on-going, and inflation has a tendency to "stick".
The extra money keeps on getting spent each year -- it doesn't affect the economy in a cumulative way. The person who used to have $0, and now has $10K to spend this year, still only has $10K next year, and still only has $10K the year after. Inflation would only continue if that person received $10K in year one, $20K in year two, $30K in year three, etc.
And inflation is a complicated thing, but it doesn't tend to stick when its causes are known, and known to be temporary. Inflation is governed by expectations, and those expectations are often unknown. In the case of UBI, it's extremely known.
(Also remember that the UBI is not new money injected into the economy -- it's generally proposed as redistribution in the form of taxation. Which according to the simplest theory wouldn't generate any inflation at all, but because of the resulting shifts in consumption patterns, that's what generates the one-time inflation among basic consumer goods, housing, etc.)
Ideally the guaranteed jobs are something more productive than paying people to dig ditches and fill them back in again. But frankly printing money to pay people to exercise 8 hours a day would probably save billions in healthcare costs.
Anyhow it’s not particularly difficult to work out a greatly more eucivic and eusocial regime than what we currently have. In fact it’s sufficiently easy that a reasonable person can only conclude that the enshittification of our societies is the intentional policy of rulers who don’t particularly care for our welfare.
Oh, wait, so you're claiming it's not a free market in reality? Suddenly those price controls don't seems like such a bad idea then.
it depends - real-estate, in general, is still very much a free market. So to your point the thing to prevent rent from just being raised is someone else undercutting you. That requires there to be adequate housing to fulfill market need which there is in many places but not everywhere. That being said... the current trend of PE firms starting to buy up real-estate for the sole purpose of renting it back to people is pretty concerning, and quite frankly shouldn't be allowed IMO. What next? Privatize the water supply and then pretend the "market will make it more efficient"?