Wanted to post this since my recent chat with Ubi-support indicated Google Authenticator is 'just an app' which is true to some extent however Yahoo carries it's own 2FA and 2SV which is separate and exclusive of Google Authenticator. Should you be greeted with the 'you have activated 2-Factor Authentication...message, and you have a yahoo email tied to your Ubisoft account, start a chat with Ubisift support and let them know whats up. Once you verify your email address with them they can turn it off for you.
Please explain further what you mean. To the best of my knowledge the system used on your Ubisoft account to setup 2FA is not altered based on the email provider you use.
If you have a smart phone and use Google Authenticator, that should have no contact with your email other than setting up the authenticator to begin with.