BuddyPress.org

@kingfisher64 Gravity form user registration addon has x-profile mapping option along with user meta values. https://www.gravityforms.com/add-ons/user-registration/
You can use it as a reference.

@kingfisher64 Not sure if that plugin has integration with BuddyPress. Since that is a paid plugin, you should be able to ask at the plugin’s forums whether it is compatible with BuddyPres. If so, how to go about the integration with BP registration. Good luck!