@leocg I used Google Authenticator. I did Not have an authenticator app associated with my account. I was able to use Google Authenticator long ago without "setting up" my account, instead, just signing-in with it. I used the same email, but at that time, the Google Authenticator app didn't have "back up codes", so I don't have access to them (assuming they exist) from the first time that I used the app. And no, I didn't "back up my accounts", didn't even know that I could, but I'm using the same account now.
I know this is lack luster, but the Authenticator app changed it's UI and it's everything. So I'm worried that I was caught in between-updates and that somehow left me in a spot where I'm stuck.
I have now set up my account on Google properly and linked my phone, but back then the app never forced me. So I never did (or even knew that I could), and thinking about it, not even sure that that was a thing back then.