iCloud Keychain got a nice update with iOS15 that enables you use it as your MFA provider. Not only does it make the likes of Google Authenticator/Authy unnecessary, it also makes for a much more seamless experience for the end user in Safari. If you have MFA enable for a service (Gmail, Reddit, etc.) you will first need to disable it. Next, locate the entry for that service in iCloud Keychain and select Setup Verification Code.
Setup:
Execution:
Bravo, Apple.