To deploy apps directly to your Chromebook, you need to do the following:

Enable ADB in Settings. Note that this requires you to reboot your
device once.

In the Terminal, run flutter devices. If prompted, authorize access to
the Android container. Verify that flutter devices lists your ChromeOS
device as a recognized device.

Set up your Android device

To prepare to run and test your Flutter app on an attached device,
you need an Android device running Android 4.1 (API level 16) or higher.

Enable Developer options and USB debugging on your device.
Detailed instructions are available in the
Android documentation.

Using a USB cable, plug your phone into your computer. On your Chromebook,
you may see a notification for “USB device detected”. Click on “Connect
to Linux” If prompted on your Android device, authorize your computer
to access your device.