The court put me on an electronic advertising screen because I owed money for materials. Is it legal?

Of course it is legal. If you don't repay your debts, you will become what people call a deadbeat. According to the law, if you have the ability to perform but refuse to perform, you may be restricted from high consumption in the future (such as flying by plane, train, going abroad, buying a house, taking a loan, etc.), you may also be detained, fined, or even refused. Execute crimes and pursue criminal responsibility.