[ccakes]

Using tools like 1Password and Bitwarden to manage your OTP codes, while arguably better than not using OTP at all, is a bad idea.

If you password for $service is exposed in a dump then you're ok but if your password manager is exposed then both factors of credentials are exposed. Using a separate app is definitely more secure.

You can use Google Authenticator without being a Google user, but Authy is another pretty reputable app which might be worth a look.