What is the ruling on investing money in an Islamic bank deposit with a variable annual profit rate of 3%, with a 2.5% zakat on the capital, leaving a net profit of 0.5%, given the absence of other investment alternatives and the lack of trustworthy individuals in the market to manage the money?

Deposits in Sharia (definition)-compliant Islamic banks are a legitimate form of mudarabah (definition) (profit-sharing investment), and the profit from them is distributed between the depositor and the bank according to their agreement. If the bank stipulates an excessive profit, it is not permissible for the depositor to resort to illicit gain, because committing what is forbidden is not allowed except out of necessity, and investing money is not a necessity.