How do I recover my Apple Account without knowing the phone number?

Hi,

Unfortunately the link we both shared shows how to recover your account *knowing* which phone number was used to create it. In my case I don't remember the phone number Apple is asking me (finishing by 29, pretty sure I never had a phone number like that and neither did I use a friend's number).

Update on my case: I notice I used the mail I'd like to be the principal as the "Notification Email":

However I cannot add it directly to my emails as it says it's not available:

Do someone knows if I remove it from the Notification Email I may then add it to the primary mail without risk of losing it? Does it mean that this gmail is linked to my apple account *without having* an independent apple account? If so I wonder why apple tells me I had a phone number finishing by 29.

[Edited by Moderator]

I already checked in all my past phone numbers and even checked in my contact list if I ever used a phone number of a friend then.

I arrived to the same conclusion that it's just not possible to recover the account without knowing which was the phone number, what a pity.