I think UBI is a lot like "Helikoptergeld" (copter money) which you distribute to everyone instead of trying to get help (money) there where it's needed.
I would absolutely just follow my dreams if I get UBI, and that won't contribute to the GDP, but rather to society.
People will be paid to scrub the toilets. (The effect on wages would be interesting: unskilled but dead-end jobs would probably see substantial wage increases, while entry-level jobs with advancement potential might see decreases, at least relative to wages overall.)
No.
I mean, if everyone paid a flat capitation equal to their UBI payment, sure, but if “everyone pays” because it is paid for out of general funds raised by a tax system which, even if it is a mix of various taxes, is approximated as a progressive tax on income, then, no, not at all.
Depending on your country's economic mix, there's almost certainly a private industry that's predictably profitable and also sort of undislodgable (for example, oil, telecom, or railways). Obvious targets for state takeover; keep the prices the same and run the profits into the state coffers, or use the pricing as an additional lever for social objectives (i. e. pricing petrol to the moon to encourage EV takeup).
Eg In Australia, there are 25M people. The annual cost of UBI per person would be around 30K (unemployment allowance) or 50K (Living wage)
This means between 750B and 1.25T in payments per year.
The current total welfare spend is approx 250B per year. Other spend is another 250B.
Funnily enough, revenue from income tax is roughly the same, around 220B.
So to pay for UBI from income taxes, would need a 300% to 500% increase across the board.
I cannot see how this happens without significant tax hikes or continuing the inflationary money printing approach.