Raycast through render texture from a graphic raycaster?

Hello all.

I am trying to make an interactive game window that's on a canvas. When I try to look up any documentation on doing this, 9 times out of 10 it is for a player camera in Unity3D.

My problem is that I'm using GraphicRaycaster.Raycast, which doesn't have access to RaycastHit.TextureCoord, unlike Physics.Raycast. So I'm not quite sure how to get a position to send a ray from my game cam. The closest thing I've seen to getting a position I need is RectTransformUtility.ScreenPointToLocalPointInRectangle, but it doesn't seem to be giving me the correct numbers.

I will keep testing and researching. Will post my results here if I find anything. Any help would be much appreciated!

 using System.Collections.Generic;
 using UnityEngine;
 using UnityEngine.UI;
 using UnityEngine.EventSystems;
 
 public class Raycaster : MonoBehaviour
 {
 
     public GraphicRaycaster mainUi;
     public EventSystem ES;
 
     PointerEventData eventData;
 
     void Update()
     {
         if (Input.GetMouseButtonDown(0))
         {     
             //Maincam Raycast
             List<RaycastResult> hits = new List<RaycastResult>();
             eventData = new PointerEventData(ES);
             eventData.position = Input.mousePosition;
             mainUi.Raycast(eventData, hits);
             foreach (RaycastResult hit in hits)
             {
                 if (hit.gameObject.tag == "GameScreen")
                 {
                     //Gamecam Raycast
 
                 }
             }
         }
     }
 }