If you encounter this page while trying to login to your Facebook account.

All you have to do is go to the main incogniton startup page, click on the name of the profile you want to login to, and copy the 'FB 2FA' text into the box at the end of the page

Paste the long 2FA text into the first box, click "Generate Key", and copy the 6-digit code generated to the Facebook login page.

2FA Generator

Enter your secret key: Generate Key

Your key: