Hello @kobakei, This fix is absolutely needed, no application can be published in .aab format without renaming the language to 'el'.

@kobakei please merge this ASAP. Using this as a temporary workaround

bundle {
    density {
        // Different APKs are generated for devices with different screen densities; true by default.
        enableSplit true
    }
    abi {
        // Different APKs are generated for devices with different CPU architectures; true by default.
        enableSplit true
    }
    language {
        // This is disabled so that the App Bundle does NOT split the APK for each language.
        // We're gonna use the same APK for all languages.
        enableSplit false
    }
}

Edit: The error message you'll see when trying to upload and AAB to play store (Feb 2020) without the above mentioned fix is as follow:

Your App Bundle targets the following unrecognized languages: gr. The list of supported language codes can be found in the IANA registry. Invalid languages caused by third-party libraries can be excluded using the resConfigs Gradle property.