Phone on registration form

Can you please check this add-on, https://www.wpdownloadmanager.com/download/advanced-custom-fields/, please let me know if it helps you

thanks

Thanks, I don’t think the site owner will like to invest the plugin for one field.
If I add the field like in the example is it saved to the user profile?

You can use https://developer.www.ads-software.com/reference/hooks/user_register/ to save the custom field and you also need to write additional code, to show the field on the edit profile page.