Recovery key is optional.
This article explains how it’s done:
How to generate a recovery key - Apple Support
CAUTION: Generating a recovery key inhibits Apple account recovery service.
You are solely responsible for maintaining your credentials; if you loose them for whatever reason, your account will become permanently inaccessible to you.
Use with caution, and I’d suggest ONLY if you have a fairly mature disaster recovery plan in-place.
i.e. if a regional natural disaster were to carry-away ALL of your trusted devices and home and office paperwork …
… can you STILL get yourself back into all your accounts starting with ONLY your memory and a browser ???