how to receive apple recovery emails when icloud email is used for apple ID and cannot access?

iPhone was glitching and we wanted to do restore from backup on Mac but was not able to. Was not able to login to Apple ID using the verification methods because the phone number on account is no longer in use and he was not signed in on other devices to receive the code.

next, we did the account recovery process but cannot check email inbox for any email confirmations or status because iCloud email is set as primary email on Apple ID.

how does he gain access to his Apple ID then?