Performing a phone migration from your old phone to your new one is super easy and will probably migrate your favourite Authenticator app across to the new phone, unfortunately that is not enough for some online accounts – eg the University OXFORD SSO MFA.
Your OXFORD SSO Microsoft Authenticator registration is linked to your current physical phone, not the app. Installing the app on a new device does not transfer your authentication methods automatically.
If you wipe or trade-in your old phone before registering the new one, you may be unable to sign in to your online accounts.