You can advertise something without value and “earn” money selling it. The perceived value was created by advertising, but didn’t actually exist.
You can raise funds, sell at a loss, buy out the competition and later drive up prices without creating any value. This is how Amazon got started.
You can go to the bank, borrow money(increasing the money supply, driving inflation, thanks to fractional reserve banking), buy up houses (driving housing inflation), and extract rent without doing anything useful for your community.
In fact, cloud computing is largely that: buying up all the compute and renting it out to those without the capital to buy themselves.
A person can create value without earning money (parenthood, volunteering), and one can earn money without creating value (rent extraction), although the word “earn” is under a lot of strain.
Money has been completely manufactured in financial markets already and doesn't seem to be screwing us over too badly. I hardly think UBI paid from taxing the largest economic surpluses and wealth in the history of the world will have a significant impact on inflation.
Any inflationary impact would happen if you print the money supply to pay UBI rather than using existing dollars in the supply.
You're also completely writing off the additional surpluses that people receiving UBI could provide if they're confident they can get by on a daily basis and also ensure they stayed healthy and working rather than spiraling any time one or two things go sideways.
But anyway, I'm not too worried about inflation mainly because of the points you raised, but I am worried about resource constrained markets like housing. If nothing is done to stop this, and I don't know how, I'm sure they'll just raise the prices to completely cancel out any UBI you'll pass around. It's not just housing either, but that's an obvious one.
I see it as exactly the opposite - culture, ethics, behavior differences etc are downstream of financial inequality. When people are financially insecure it becomes much harder to tolerate disagreement, and much easier to blame [insert whatever populist notion of enemy]. I think it would be easier to engage with people with opposing ideas, not seeing them as an existential threat, if you are not worried about housing, income or health insurance.
Cultural polarization is a deflection mechanism (both in the subconscious psychological sense as well as a politcal/propaganda technique) meant to mask the real deeper structural inequalities. It's the lie we tell ourselves and the powers that be tell us to prevent to change the direction of the "wealth redistribution" we've been witnessing for 20+ years.