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 AndO

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.