Because GitHub obeys the part of the spec. which says sites need to allow multiple credentials, you should still be able to get where you're going (I haven't seen this "Hello" pathway) via a circuitous route.

1. Let the Hello stuff happen, GitHub will propose that you name it, why not "Hello".

2. Tell GitHub you want to enroll another token. The system will automatically disregard "Hello" because that was already enrolled, so this time it will enroll your Yubikey or whatever other tokens.

3. (Optionally, if you don't want "Hello" e.g. because it isn't your Windows PC you just borrowed it) Tell GitHub you want to remove "Hello".

With which browser?

This was a while ago, so I don't quite remember. Either Chrome or Firefox.