Because in Unity/C# UnityApplication.systemLanguage doesn't support Hindi, you can use this C# code snippet to recognize a Hindi system language

UnityApplication.systemLanguageHindiFix.cs

//NOTE: This only works for Android

using (AndroidJavaClass cls = new AndroidJavaClass("java.util.Locale"))
{
      using (AndroidJavaObject locale = cls.CallStatic<AndroidJavaObject>("getDefault"))
      {
            if (locale.Call<string>("getDisplayLanguage") == "हिन्दी")
            {
                //HINDI
            }
      }
}