Call them to follow up. Ask them to provide candid feedback b/c you want to learn and adapt based on their feedback. If they chose someone else, ask what that person had that you didn't. Be very kind so they don't feel like they have to be defensive. If you say, "I'd be so appreciative if you'd be willing to give me some candid feedback about my interview, it would mean the world to me b/c I want to learn from this process." Reiterate your interest in the role and ask if they have any other suggestions for you to pursue work in this field. Good luck!