How can I trigger the select menu on product page from another button to update variant information

I want to use a custom input button that when clicked, will update the select menu option ( the default variant options menu that shows up on the debut theme ) and update the variant info on the product page. I’m using the debut theme.

How do I achieve this? using an onclick event on the button and update the value of the select only changes the option of the select menu but doesn’t trigger the event the select has to update the variant info