System initializer for Unity taken from Tarodev (https://www.youtube.com/watch?v=zJOxWmVveXU)

SystemsLoader.cs

using UnityEngine;

public static class SystemsLoader
{
    [RuntimeInitializeOnLoadMethod(RuntimeInitializeLoadType.BeforeSceneLoad)]
    public static void Execute()
    {
        var systems = Resources.Load("Systems");

        if (!systems)
            return;
        
        Object.DontDestroyOnLoad(Object.Instantiate(systems));
        Debug.Log("Systems Loaded");
    }
}