I need help fixing my Flutter VPN app's build configuration for Amazon Appstore submission

PROBLEM:
- Uploading app to Amazon Appstore
- Getting error: "AAB2 bundle currently supports no devices"
- AAB1 works fine (supports 12 Fire Tablets + 2 Fire TV)
- AAB2 bundle is being rejected

WHAT I NEED:
- Fix build.gradle.kts to generate single universal AAB with ARM support only
- Ensure app supports all Fire Tablets and Fire TV devices
- Remove x86/x86_64 architectures that Fire devices don't need
- Test build to confirm it works

TECHNICAL DETAILS:
- Flutter app with Kotlin DSL (build.gradle.kts)
- Need to configure NDK abiFilters correctly
- Currently using default Flutter build settings
- App already has proper signing and ProGuard configured