If you have not done so already, we would highly suggest downloading the Authy app for all 2FA purposes. You would not have to deal with SMS delays in receipt of activation codes, or any of the inherent security vectors presented by SMS.
Search for "Authy" in your mobile device's app store and download the app. Once downloaded, open the app on your phone to see your Gemini account already loaded. There is no need to scan a QR code as we have a direct integration with Authy - everything happens behind the scenes. We recommend disabling the multi-device option. Disabling the multi-device option safeguards your Authy account even if your phone number is targeted by a successful phone porting attack.
Unfortunately, we only offer 2FA via Authy or SMS at this time. We will let you know if we decide to integrate Google Authenticator or any other form of verification for 2FA.