QE did not dump trillions into the system. It was very targeted, and as it turns out, mostly useless, because it didn’t get banks to lend.
What most are talking about re UBI is giving EVERYONE money. If you give everyone money, then all of that spending will cause a ramp in prices. period. that is exactly how economics work.
And because it would all be financed by debt, you’d have a rise in interest rates (maybe even a spike), which then makes everything more expensive.