...What should I do? Any other ways to earn free money?
Based on the fact that you hold BNB, it means that you fully trust the Binance exchange. Therefore, you should not take them outside the exchange, despite the apparent simplicity in additional earnings. There are enough programs on Binance that allow you to earn extra income for holding BNB, and they are 100% legal.
yes you are right, you can earn passive income just by holding BNB coins. and this method is among the easiest and we don't have to pay too much attention to this.