Hi,

In that topic described a possible way to achieve that:

https://mdbootstrap.com/support/react/correct-way-to-validate-mdbselect-in-react-form/.

You can add ahandleSubmit function to the form's button. In that function, you can check if any value is selected. By default value is Choose your option, so you can compare selected value to Choose your option. If the condition is true than use e.preventDefault() so your form will not be submitted and you can show to a user an error message.

handleSubmit = (e) => {
        if (this.state.value === 'Choose your option') {
            e.preventDefault();
              ....
        }
    };

Best regards.