⌘K

Change app name

Change the value of label from <project>/android/app/src/main/AndroidManifest.xml
android:label="My App"

Change the value of CFBundleName from <project>/iOS/Runner/info.plist
<key>CFBundleName</key>
<string>My App</string>

Uninstall the previous apk and rebuild again

Change app name in system tray

Go to <project>/lib/main.dart

Change the value of ‘title’ as you wish