When you set up 2FA, you will be a shown a QR code to scan with the Aegis app. You will also be shown a 16 character back up code made up of numbers and letters.
This may differ from operative system, I am basically using Android for this.
On Google 2FA, no secret character again along with QR code as it was before. All there now is a QR code which can be exported.
On Aegis, I also thought I have seen the secret character along with QR code before but it is not there when I checked it recently. Probably this has changed in few released latest versions.
The easy means I used to get the secret code for backup is the method I
explained above, but I prefer the .txt and delete it from my devic after I backup it offline. You can clearly see each secret character if the .json or .txt for the unencrypted format. Or making use of scanner directly to also reveal the secret code for offline backup, I tried a scanner and it also work as fine.