Currently,
My team and I are developping an Android Auto enabled app. And it appears to me this app is only available in my car unit, when I enable unknown sources in the Android Auto app.
However I'm wondering what defines an unknown source and how do I make sure my app is not an unknown source. Does Android Auto communicate with the Google Play Services for this or do i need to sign the APK with specific data?
How are you deploying your app? If you are deploying with Android Studio: as I recall you won't see it on your real automotive head unit, just the emulator. To show on the head unit it needs to be deployed in the Play Store, at least in developer and pre-release mode while under development.
First of all: Android Auto runs on your own device, meaning it adapts the same permissions you granted to particular apps. If your app doesn't have an app in the normal UI or you didn't open it on your phone once, then it would usually prompt you to grant permissions the first time you open it.
An unknown source is pretty much any way of getting your app outside of the Google Play Store (and OEM-specific app stores like Samsung App Store for Samsung devices etc.).
That is especially common if you e.g. download an .apk from the internet and want to install it, but your phone thinks their own file manager is an unknown source (because it is not intended to download apps).
