Since I want to add Firebase to my Android Game I want to include Google Auth. But I have the following Problem. I need to add some Code to the build.gradle File but I cant
From Unity v2018.3 onwards, you can add your own custom Gradle build file by simply enabling the Custom Gradle Template property on the Player window (which can be accessed by File > Build Settings > Player Settings > Publishing settings). This generates a default mainTemplate.gradle file for you, which you can edit.
It will be in the location: Assets/Plugins/Android/mainTemplate.gradle
Source: https://docs.unity3d.com/Manual/android-gradle-overview.html
To use Gradle in Unity.
1.Go to <UnityInstallationDirecory>\Editor\Data\PlaybackEngines\AndroidPlayer\Tools\GradleTemplates
, then copy mainTemplate.gradle
file to your <ProjectName>Assets\Plugins\Android
folder.
2.You can then modify mainTemplate.gradle
to be whatever you want it to be. Now, to make sure the build uses the gradle file, change the Build System to "Gradle (New)".