Flutter: ElevatedButton has different theme on Linux

Problem

I have a Flutter application that uses an ElevatedButton widget.
When I run the application on Windows the button colors are fine, but when I run it on Linux, they are different.

Here's my code :

ElevatedButton(    onPressed: () {        // ...    },    child: Container(        alignment: Alignment.center,        height: 60,        child: const Text("Avvia",            style: TextStyle(                fontSize: 26,                fontWeight: FontWeight.bold,            ),        ),    ),),

Result

On Windows:

On Linux (Kali Linux on WSL):

Does anybody know why it happens and how can I fix it?