The App ID you registered on App Store Connect.

In the Deployment info section:

The minimum macOS version that your app supports. Flutter supports macOS 10.11 and later.

In the Signing & Capabilities section:

Whether Xcode should automatically manage app signing
and provisioning.  This is set true by default, which should
be sufficient for most apps. For more complex scenarios,
see the Code Signing Guide.

Select the team associated with your registered Apple Developer
account. If required, select Add Account…,
then update this setting.

The General tab of your project settings should resemble
the following:

For a detailed overview of app signing, see
Create, export, and delete signing certificates.

Configuring the app’s name, bundle identifier and copyright