Google Authenticator supports TOTP, and not only for their own 2-step verification but one can "Manually add" other accounts.
The bridging part from TOTP to OpenID, in my case, comes from Clavid (cf. OTP@Clavid).
Now to the tiny bit of information that might save you quite some minutes: when entering your secret key into these two locations to set-up an account
- Google Authenticator expects the string to be RFC4648 Base32 encoded
- Clavid expects the string to be hex encoded