Maybe it's different in the US, but in many EU banks you now have to use the app for 2FA. Some banks offer alternatives but many don't.
I'm not aware of any US bank that *requires* an app. This rules out access from a desktop doesn't it?
You use the same procedure you used to register that phone, to register a new one.
> This rules out access from a desktop doesn't it?
Using the phone for 2FA means you are accessing from a desktop, and using the phone only as an extra confirmation for the transaction.
May not be possible if you need your old phone to login.
This reminds me of Internet Service Providers who direct you to get support online when failure to get online is the very reason why you need support.
If your phone die, you replace it or do your operations at the ATM or at the counter during opening hours.
Replacing it is the problem. This can't be done at an ATM and if you're on a trip or you use an online bank, a counter may not be available.