Seems fine. Displays my ugly default dashboard and works as expected. Little bit of a pain to get it built, but I've never created an Android app so that might just be my inexperience. I happened to have the Android SDK installed, but still needed some manual steps. Basically:
Get the Flutter SDK. I extracted it to %LOCALAPPDATA%\Android\Sdk\flutter.
From the command line, change your working directory to wherever you cloned the repository.
Run %LOCALAPPDATA%\Android\Sdk\flutter\bin\flutter.bat build apk (in Windows, anyway).
Install the application on your phone with %LOCALAPPDATA%\Android\Sdk\platform-tools\adb.exe install build\app\outputs\flutter-apk\app-release.apk
I ran the build command in Android Studio, but I'm not sure if that's necessary. I opened the repository's android folder as an existing project. When all is said and done, I get this output from the build.
Running "flutter pub get" in hubitat-simple-dashboard... 10.5s
Building without sound null safety
For more information see https://dart.dev/null-safety/unsound-null-safety
Note: %LOCALAPPDATA%\Android\Sdk\flutter\.pub-cache\hosted\pub.dartlang.org\location_permissions-3.0.0+1\android\src\main\java\com\baseflow\location_permissions\LocationPermi
ssionsPlugin.java uses or overrides a deprecated API.
Note: Recompile with -Xlint:deprecation for details.
Note: Some input files use or override a deprecated API.
Note: Recompile with -Xlint:deprecation for details.
Running Gradle task 'assembleRelease'...
Running Gradle task 'assembleRelease'... Done 112.2s
√ Built build\app\outputs\flutter-apk\app-release.apk (16.0MB).