After 1Password has filled the username and password field for my WP installation (or any other website where two factor is on), the field for the two factor authentication opens, asking for the six numbers from the Authenticator App, or from a message. It's a bit confusing that 1Password then acts again, giving suggestions to fill in.
1Password Version: 7.8.7 (70807004)
Extension Version: 22.214.171.124
OS Version: Big Sur 11.5.2