They could always copy the British. Savings accounts are allowed, but you can only save a certain amount (£6000 last time I checked) before your UBI starts getting cut. It’s great for the banks, but next to useless for anyone on welfare or in the working classes (For me it’s three months rent, food and bills, at best).
Rich people will just put their extra money into a trust so they can keep getting the full UBI while still having access to the rest of their money.