How to set @icloud.com mail alias as your Apple ID?
An Apple account is identified by its Apple ID, which for a long standing account, has a lot of information associated with it. However, people grow up, get married, change their names. Not everyone wants to set up a new Apple ID when that happens. However, an account handle set up years ago can become irrelevant over time.
Apple IDs can already be changed if you use a 3rd party email address or have a mail alias that ends in @me.com or @mac.com (https://support.apple.com/en-us/HT202667#appleaddress). However, how do you do the same for a mail alias that ends in @icloud.com?