Preloads all GameObjects from _preloader scene and makes them DDOL automatically

ScenePreloader.cs

using UnityEngine;
using UnityEngine.SceneManagement;

public class ScenePreloader : MonoBehaviour
{
    [RuntimeInitializeOnLoadMethod(RuntimeInitializeLoadType.BeforeSceneLoad)]
    static void OnBeforeSceneLoad()
    {
        LoadPreloaderScene();
    }

    void Start()
    {
        GameObject[] rootObjects = SceneManager.GetSceneByName("_preloader").GetRootGameObjects();
        foreach (GameObject rootObject in rootObjects)
            DontDestroyOnLoad(rootObject);
        Destroy(gameObject);
        SceneManager.UnloadSceneAsync("_preloader");
    }

    static void LoadPreloaderScene()
    {
        for (int i = 0; i < SceneManager.sceneCount; i++)
        {
            Scene scene = SceneManager.GetSceneAt(i);
            if (scene.name == "_preloader")
                return;
        }

        SceneManager.LoadScene("_preloader", LoadSceneMode.Additive);
        GameObject go = new GameObject("_PRELOADER");
        go.AddComponent<ScenePreloader>();

        SceneManager.MoveGameObjectToScene(go, SceneManager.GetSceneByName("_preloader"));
    }
}