Can I create Flutter project offline?

You can try to enable Gradle (Androud build system by default) Offline Mode. For more information you need to describe situation when you need to use Offile Mode.

Desktop support allows you to compile Flutter source code to a native Windows, macOS, or Linux desktop app. Flutter’s desktop support also extends to plugins—you can install existing plugins that support the Windows, macOS, or Linux platforms, or you can create your own.

You need an internet connection to download Gradle dependencies , errors points to no network when trying to download these dependencies.