How to randomize non-repaeting question?

Hi, I`m making a quiz game following official live training tutorial and I would like to set it up so that the questions are showing up randomly in that way that they are not repeating in the currentRound of quiz. I saw in comments of that tutorial that author said we could use Shuffle bag technique but that is a little bit too complicated to implement. Is there any other simpler way to do it? Here`s a script from that tutorial that contains ShowQuestion method:

 using UnityEngine;
 using UnityEngine.UI;
 using UnityEngine.SceneManagement;
 using System.Collections.Generic;
 
 public class GameController : MonoBehaviour
 {
     public SimpleObjectPool answerButtonObjectPool;
     public Text questionText;
     public Text scoreDisplay;
     public Text timeRemainingDisplay;
     public Transform answerButtonParent;
 
     public GameObject questionDisplay;
     public GameObject roundEndDisplay;
     public Text highScoreDisplay;
 
     private DataController dataController;
     private RoundData currentRoundData;
     private QuestionData[] questionPool;
 
     private bool isRoundActive = false;
     private float timeRemaining;
     private int playerScore;
     private int questionIndex;
     private List<GameObject> answerButtonGameObjects = new List<GameObject>();
 
     void Start()
     {
         dataController = FindObjectOfType<DataController>();                                // Store a reference to the DataController so we can request the data we need for this round
 
         currentRoundData = dataController.GetCurrentRoundData();                            // Ask the DataController for the data for the current round. At the moment, we only have one round - but we could extend this
         questionPool = currentRoundData.questions;                                            // Take a copy of the questions so we could shuffle the pool or drop questions from it without affecting the original RoundData object
 
         timeRemaining = currentRoundData.timeLimitInSeconds;                                // Set the time limit for this round based on the RoundData object
         UpdateTimeRemainingDisplay();
         playerScore = 0;
         questionIndex = 0;
 
         ShowQuestion();
         isRoundActive = true;
     }
 
     void Update()
     {
         if (isRoundActive)
         {
             timeRemaining -= Time.deltaTime;                                                // If the round is active, subtract the time since Update() was last called from timeRemaining
             UpdateTimeRemainingDisplay();
 
             if (timeRemaining <= 0f)                                                        // If timeRemaining is 0 or less, the round ends
             {
                 EndRound();
             }
         }
     }
 
     void ShowQuestion()
     {
         RemoveAnswerButtons();
 
         QuestionData questionData = questionPool[questionIndex];                            // Get the QuestionData for the current question
         questionText.text = questionData.questionText;                                        // Update questionText with the correct text
 
         for (int i = 0; i < questionData.answers.Length; i ++)                                // For every AnswerData in the current QuestionData...
         {
             GameObject answerButtonGameObject = answerButtonObjectPool.GetObject();            // Spawn an AnswerButton from the object pool
             answerButtonGameObjects.Add(answerButtonGameObject);
             answerButtonGameObject.transform.SetParent(answerButtonParent);
             answerButtonGameObject.transform.localScale = Vector3.one;
 
             AnswerButton answerButton = answerButtonGameObject.GetComponent<AnswerButton>();
             answerButton.SetUp(questionData.answers[i]);                                    // Pass the AnswerData to the AnswerButton so the AnswerButton knows what text to display and whether it is the correct answer
         }
     }
 
     void RemoveAnswerButtons()
     {
         while (answerButtonGameObjects.Count > 0)                                            // Return all spawned AnswerButtons to the object pool
         {
             answerButtonObjectPool.ReturnObject(answerButtonGameObjects[0]);
             answerButtonGameObjects.RemoveAt(0);
         }
     }
 
     public void AnswerButtonClicked(bool isCorrect)
     {
         if (isCorrect)
         {
             playerScore += currentRoundData.pointsAddedForCorrectAnswer;                    // If the AnswerButton that was clicked was the correct answer, add points
             scoreDisplay.text = playerScore.ToString();
         }
 
         if(questionPool.Length > questionIndex + 1)                                            // If there are more questions, show the next question
         {
             questionIndex++;
             ShowQuestion();
         }
         else                                                                                // If there are no more questions, the round ends
         {
             EndRound();
         }
     }
 
     private void UpdateTimeRemainingDisplay()
     {
         timeRemainingDisplay.text = Mathf.Round(timeRemaining).ToString();
     }
 
     public void EndRound()
     {
         isRoundActive = false;
 
         questionDisplay.SetActive(false);
         roundEndDisplay.SetActive(true);
     }
 
     public void ReturnToMenu()
     {
         SceneManager.LoadScene("MenuScreen");
     }
 }