UnityWebRequest with "text/event-stream" header doesn't work in webgl build

Hi!

I am trying to implement a request to firebase, which follows server side events protocol. It looks like this:

 using System.Collections;
 using UnityEngine;
 using UnityEngine.Networking;
 
 public class Test : MonoBehaviour
 {
     public IEnumerator TestCoroutine()
     {
         string databaseSecret = "DATABASE_SECRET";
         string firebaseHost = "https://your-firebase-project.firebaseio.com";
         UnityWebRequest req = UnityWebRequest.Get(firebaseHost + "/.json?auth=" + databaseSecret);
         req.SetRequestHeader("Accept", "text/event-stream");
         var response = req.SendWebRequest();
         while (!req.downloadHandler.isDone)
         {
             Debug.Log("Text downloaded: " + req.downloadHandler.text);
             yield return new WaitForSeconds(1);
         }
     }
     // Use this for initialization
     void Start()
     {
         StartCoroutine(TestCoroutine());
     }
 }

It works fine in editor, but no data is received in webgl build. With webgl build I can see in browser dev tools that the request is made, and that it continues running, so req.downloadHandler.isDone is false, however both req.downloadHandler.text and req.downloadHandler.data are always empty. I tried using wireshark to see if any data is passed and I observed that there are new chunks of data when the server side event is triggered by me, using another device, but it's hard to tell what this data represents - its not readable.

I wanted to know if I am doing something wrong, of it is a bug or if it is a limitation of webgl. I would appreciate suggestions on workaround. Thanks!