Keywords: Unity, Basic Usage

From scratch

C# Script (Thanks for Jaakko Saaristo):

using System.Collections;
using UnityEngine;

public class ScreenLogger : MonoBehaviour {

    private string log;
    private const int MAXCHARS = 10000;
    private Queue myLogQueue = new Queue();
    void Start() {
        Debug.Log("Screen logger started");
    }

    void OnEnable() {
        Application.logMessageReceived += HandleLog;
    }

    void OnDisable() {
        Application.logMessageReceived -= HandleLog;
    }

    void HandleLog(string logString, string stackTrace, LogType type) {
        myLogQueue.Enqueue("\n [" + type + "] : " + logString);
        if (type == LogType.Exception)
        myLogQueue.Enqueue("\n" + stackTrace);
    }

    void Update() {
        while (myLogQueue.Count > 0)
        log = myLogQueue.Dequeue() + log;
        if (log.Length > MAXCHARS)
        log = log.Substring(0, MAXCHARS);
    }

    void OnGUI() {
        GUILayout.Label(log);
    }
}

Reference:
Print debug.log to screen? C#
https://answers.unity.com/questions/1020051/print-debuglog-to-screen-c.html

Using plugin

A simple and fully customizable screen logger. Just put it on a scene and you will see on screen output for each call to Debug.Log/LogWarning/LogError.
https://assetstore.unity.com/packages/tools/gui/screen-logger-49114

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