Apple Account locked due to inaccessible two-factor authentication number

Hello. I need assistance please. I have a second iCloud account for another iPhone device and I no longer have access to the mobile number registered under the iCloud account on that device. Unfortunately, the two-factor authenticator is active. But there is no way I can get a code at that number because I no longer own the number and I don't know who got it. Each time I try to login to my account to change the phone number, Apple still keeps asking me to enter the number to receive the code at. Even when I select that I have no access to the number, it still takes me to a page where I have to enter the phone number. I don't even remember the phone number because I had it more than 6 years ago when I was in Saudi Arabia. Now I decided to login to my iCloud on that device and I curse the moment I activated the two factor authentication. Apple should give an option to report that I no longer have access to the mobile number and therefore there should be some other way I get the code. It is MY account. They can verify that with my passport and the photos in my account, if need be. I cannot even reach Apple support because I cannot download Apple Support App on that device! Any guidelines to follow?

[Re-Titled by Moderator]

Original Title: No longer have access to my registered mobile number