No option to add a phone number as a sign-in alias under “Manage how you sign in”

On my Microsoft account page, clicking “Your info” > “Edit account info” takes me to the “Manage how you sign in” page. From what I understand, I should be able to add a phone number there and use it as an account username/alias. However, it seems there may be an issue with the current system: only email addresses can be added, and there is no option to add a phone number. As a result, I can’t add or change a phone number. I’m not sure whether this is now the standard behavior for everyone or whether something is wrong. How should this be configured? What steps should I take? Does it need to be enabled by an administrator? Please help me look into this. Thank you.

I also suggest improving this area in the future. For a company as large as Microsoft, this simple settings page is surprisingly confusing. For example, after I sign in to one account, it sometimes gets mixed up with another account, and both accounts are shown together, so I don’t know which one I’m actually working with. I won’t go into that here.