Support standard 2FA

I don't know which app you're talking about.  But feel free to submit feature requests to Adobe UserVoice.  That's where product developers will see it. 

https://helpx.adobe.com/x-productkb/global/how-to-user-voice.html

I don't understand why Adobe decided that the best way to solve a security problem was to make up something completely new and different instead of using the existing Time-based One-time Password Algorithm (TOTP) standard that is already widely supported and most users will already be familiar with. A number of the standard apps do support backup/recovery.

I do not trust or like Adobe's phone app. Aside from the fact that it is an entire app that does nothing other than 2FA for a single account, there is also Adobe's long history of failure when they have invented their own closed, non-standard security solutions, and they have a history of compromised and disclosure of user data.

If your phone is setup to display SMS in the lock screen or if you are worried you will loose or destroy your phone, then you should probably choose the email option. This is the least convienient. However, if you are using Microsoft or Google clouds for email, then you can be sure you email is not going to be hacked unless you are careless with your own security.