Tax deduction for welcome bonus / bonus “€100” at comdirect for opening a depot

Hello, a question for the tax specialists: I took part in a comdirect depot promotion. A €100 bonus was promised for opening a securities account including deposit and advertising consent: "You will receive a bonus of €100 as a savings plan subsidy. The savings plan must be opened within the first 3 months after the account was opened and the savings plan must be executed at least once. In addition, consent must be given during the opening of the account