Pick image from android gallery

So this has been asked before but there was no answer except for go buy someones asset, which is unacceptable for me because I need to know how to do it.

I'm working entirely from c# using AndroidJavaClasses, AndroidJavaObjects and AndroidJavaProxies. My current code is below with my three failed solutions.

Anyone got any ideas??

 using UnityEngine;
 using UnityEngine.UI;
 
 public class ImagePicker : MonoBehaviour {
 
     class OnActivityResultCallback : AndroidJavaProxy {
         public Text textbox;
 
         public OnActivityResultCallback() : base("android.app.Activity") {
         }
 
         protected void onActivityResult(int requestCode, int resultCode, AndroidJavaObject intent) {
             textbox.text += "onActivityResult: " + requestCode;
         }
 
     }
 
     public Text textbox;
 
     public void RequestImageFromGallery() {
 
         AndroidJavaClass intentClass = new AndroidJavaClass("android.content.Intent");
         AndroidJavaObject intentObject = new AndroidJavaObject("android.content.Intent");
 
         intentObject.Call<AndroidJavaObject>("setAction", intentClass.GetStatic<string>("ACTION_GET_CONTENT"));
         intentObject.Call<AndroidJavaObject>("setType", "image/*");
 
         OnActivityResultCallback callback = new OnActivityResultCallback();
         callback.textbox = textbox;
 
         // Solution 1, use the Unity current activity, problem: no onActivityResult to return result to
         AndroidJavaClass unity = new AndroidJavaClass("com.unity3d.player.UnityPlayer");
         AndroidJavaObject UnityActivity = unity.GetStatic<AndroidJavaObject>("currentActivity");
         UnityActivity.Call("startActivityForResult", intentObject, 1);
 
         // Solution 2, use a AndroidJavaProxy with onActivityResult implemented, problem: there is no activity instance in a proxy and so gives an error about application threads being null
         callback.Invoke("startActivityForResult", new object[] { intentObject, 1 });
 
         // Solution 3, use java reflection from c# to call the startActivityForResult method with the callback as the "this" object, problem: I get an error when trying to get the getMethod method and I'm not sure it'll work anyway
         // class intClass = java.lang.Integer.class; (ish)
         AndroidJavaClass intClass = new AndroidJavaClass("java.lang.Integer");
         // java.lang.Class jclass = obj.getClass();
         // java.lang.reflect.Method method = jclass.getMethod(methodName, param1.class, param2.class, ..);
         AndroidJavaClass jclass = UnityActivity.Call<AndroidJavaClass>("getClass");
         AndroidJavaObject method = jclass.Call<AndroidJavaObject>("getMethod", "startActivityForResult", intentClass, intClass);
         // method.invoke(obj, arg1, arg2,...);
         method.Call("invoke", callback, intentObject, 1);
 
     }
 
 }