[eat_veggies]

It's a weird variant of TOTP, but you have to be rooted or modify the app in order to extract the secret to use with other apps. Years ago I wrote a script to do it, but I'm not sure if it still works -- it's not really worth doing imo

https://github.com/steamguard-totp/steamguard-shared-secret

[MayeulC]

The issue is that the app uses a custom protocol to confirm Steam community transactions (Steam inventory trades, etc). So if you use an authenticator like AndOTP, you lose the ability to confirm those.

I reverted to e-mail. I only have free software on my phone, and don't regret that choice.

[jannes]

Unfortunately, you can't use Steam Guard without a phone number.