Google makes using a different TOTP authenticator very difficult.

First, I need to register a phone number as 2FA. Only then can I choose an alternate method, get codes, and have to select Google Authenticator to use my Open Source authenticator, Aegis.

Does not say Google Auth or any TOTP; specifically only says Google Auth. I was worried Aegis would not work until I tried it.

Why not show choices on the sign up screen? Why do I need to register a phone number first? It is very insecure in the USA. Data collection? Hold out from when a phone number was the only real 2FA and a TOTP was under additional options? If the latter, that needs to change if 2FA is going to be mandatory.