So, not sure why that support article is still out there, nor do I remember ever seeing the ability to create a Recovery Key for Two-Factor.
You need to update your Trusted Phone Numbers to include additional phone numbers where you would be able to receive a Verification Code. The phone numbers can be any type of mobile phone or landline. So, if you do not have any other devices or computers that you have signed into iCloud with your Apple ID, then you can add phone numbers of people you trust who would be able to receive the Verification code for you and relay it to you - your Mom, friend, sibling, etc. I have both my numbers and my husband's number in my Trusted Number list and vice-versa. We also both have our home phone landline number in our Apple accounts.
See this support article for Two-Factor Authentication: Two-factor authentication for Apple ID - Apple Support
And this one for recovering your account if you cannot get a verification code and have only one Trusted Device: Recover your Apple ID when you can’t reset your password - Apple Support
I'll alert the Hosts about the article you provided to see if it can't be yanked from the active articles.
Thanks for linking it!
Best,
GB