Why is my phone number unavailable for sharing in sign-in & security on my iPhone
why is my phone number unavailable for sharing in sign-in & security on my iphone
[Re-Titled by Moderator]
One phone number per Apple ID on one iPhone, except if you have a iPhone that has two eSIMs. You could then theoretically sign into two separate iCloud accounts, but with separate phone numbers.
Set up Family Sharing on iPhone - Apple Support (CA)