Not necessary the account recovery is to be done every time , if one remember the old trusted number ( say 1234.... ) that is inactive , the person can visit the cellular service give his identification proof and issue a sim on behalf of the same number and insert the sim Set up cellular service in new iPhone that is purchased
Turn on and set up iPhone
The Apple ID and password is active so is the 2FA active on the iCloud server , once a new trusted number is added the code will start appearing on the new trusted number , and the person can access the account .
See the article https://support.apple.com/en-us/HT204974
The Apple ID say example1@icloud.com exists on server and you know the password and its account credentials , however that is not signed in the device iPhone / Mac / iPad .
If you don't remember the trusted number and yet it is verified in the account , visit your cellular service centre with personal identification proofs , the number can be obtained from them .
If the account is set with two factor authentication from iPhone .
Issue a sim on behalf of the same number and insert the sim Set up cellular service on iPhone - Apple Support
In a new iPhone that is purchased Turn on and set up iPhone - Apple Support
The Apple ID and password is active so is the 2FA active on the iCloud server , once a new trusted number is added the code will start appearing on the new trusted number , and the person can access the account .
See the article Get a verification code and sign in with two-factor authentication - Apple Support
Then access the account and remove an old inactive verified number from the account .
Go to your Apple ID account page and enter your Apple ID and password.
In the Security section, click Edit.
Click Add a Trusted Phone Number.
To add a number, enter the phone number and verify it with a text.
To remove a number, click cross sign next to the phone number you want to remove.
Note : you don't need account recovery from the server as Apple ID and password are known to you How to use account recovery when you can’t reset your Apple ID password - Apple Support
The account was not set up with secondary authentication in which three answers for respective questions , rescue mail address and its password , date of birth is added .