International Telephone Input integration for Magento 2.
https://magery-themes.com/intl-tel-input-magento2.html

Module covers two different areas: UI components and regular forms.
Integration points:

Layout handle	Details
checkout_index_index	All checkout components
contact_index_index	Contacts form
customer_account_create	Customer registration form: custom attributes (Enterprise Edition)
customer_account_edit	Customer edit form: custom attributes (Enterprise Edition)
customer_address_form	Customer address form: billing and shipping addresses, custom address attributes (Enterprise Edition)
multishipping_checkout_customer_address	Ship to multiple addresses
company_account_create	Company registration form (Enterprise Edition - B2B)
company_index_index	Company edit form (Enterprise Edition - B2B)
company_profile_edit	Company profile edit form (Enterprise Edition - B2B)
company_users_index	Manage company users (Enterprise Edition - B2B)
magento_giftregistry_index_edit	Gift registry form (Enterprise Edition)