How can I sign in to a device running an old version of iOS (6.1.3) with my Apple ID when it requires two factor authentication?

I have a iPhone 4s that, at the moment, is running iOS 6.1.3. I want to sign in using MY Apple ID. Every time I type my credentials in, it says I need to enter the six digit passcode. Fine, I think. So I go fetch my iPhone 5s (running iOS 12.3.1), and it gives me a perfectly good six digit code. I then try to type it in to my 4s, but wait, there's no six digit code input field.

So I went looking for a solution to maybe disable two factor authentication, but that seems to be impossible. So I'm left with one possible solution now, asking the community!