How to sign in when you don’t have other devices
How do I sign into my iCloud if I don’t have the device that has the number that sends the verification code to?
iPhone 6s
You have lost the trusted device / damaged ... that was added in 2FA .
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 https://support.apple.com/en-in/guide/iphone/iph3f11fba92/ios in new iPhone that is purchased https://support.apple.com/en-in/guide/iphone/iph1fd7e482f/ios
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/HT204974https://support.apple.com/en-in/guide/mac-help/mchlf24d4e49/1
