Reading your post gave me flashbacks to Weird Al's Albuquerque. Then I had to go listen to it. That was fun :-)

If you're asking how to get back into your GitHub account, GitHub gives you a list of one-time passwords when you enable 2FA, specifically for the purpose of recovering your account after losing the 2FA device. Maybe this jogs a memory? Maybe you wrote them down somewhere, in an encrypted file or on a piece of paper in a desk drawer? Aside from that, you might be able to contact support and use your email to get back in, especially if you're a paying customer. (or become a paying customer)

If you're asking for best practices going forward, I'd suggest writing down those OTP codes in both an encrypted password safe, like KeePass, and also on paper in the back of a desk drawer. The choice of OTP mechanism is personal preference, but there are Fido-based hardware keys like the YubiKey (what I use) and the Google Authenticator app for phones or tablets.

I'm not sure why your SSH key expired - I've been using mine since forever. I guess I should probably rotate it from time to time, but its 4096 bit so probably fine. The SSH key won't get you into the GitHub user interface though.