Just being born in some geographical location doesn’t make you a decendant of their people. You are a decendant of where your ancestors are from. If your family doesn’t celebrate their heritage then pick the one that best describes where they come from. Maybe sit down and ask your parents or grand parents some questions about your ancestry so you can come to an identity based on facts.
Did you bother to contact their customer support asking if they plan to add this feature?
In my biased opinion, I would imagine Gmail would want to use you and your emails for every ounce of data they can squeeze out of it. However proton is a paid service who doesn’t sell your data, with much less Human Resources than google, therefore less language support. They add things as fast as they can get around to them. If you inquire they might be more apt to add the support if they have someone on staff that can do it.