It's still broken, but I made a bit of progress.

RelayClient/Resources/Raw/wwwroot/index.js

@@ -1,4 +1,4 @@
-let peerConnection = null;
+let peerConnection = null;
 let localStream = null;
 let currentUsername = null;
 let currentChannelId = null;
@@ -26,6 +26,30 @@ window.setChannelId = function(channelId) {
     LogMessage("Channel set to: " + currentChannelId);
 };
 
+//window.AnswerCallback = async function(answer) {
+//    try {
+//        LogMessage("AnswerCallback called with: " + JSON.stringify(answer));
+//
+//        if (!peerConnection) {
+//            await ensurePeerConnection2();
+//        }
+//
+//        if (!answer || !answer.type || !answer.sdp) {
+//            LogMessage("AnswerCallback received invalid answer");
+//            return;
+//        }
+//
+//        await peerConnection.setRemoteDescription({
+//            type: answer.type,
+//            sdp: answer.sdp
+//        });
+//
+//        LogMessage("Remote answer applied");
+//    } catch (err) {
+//        LogMessage("AnswerCallback failed: " + err);
+//    }
+//};
+
 function LogMessage(msg) {
     const messageLog = document.getElementById("messageLog");
     messageLog.value += '\r\n' + msg;
@@ -218,16 +242,21 @@ async function ensurePeerConnection2()
             `ICE connection state change: ${peerConnection.iceConnectionState}`);
     });
 }
+
 async function channelCallJoin(activeCall)
 {
     LogMessage("Active call: " + activeCall);
+
     await ensurePeerConnection2();
-    
+    await ensureLocalMedia();
+
     if (activeCall)
     {
         const rawJson = await window.HybridWebView.InvokeDotNet("GetRtcOffer");
         const offer = typeof rawJson === "string" ? JSON.parse(rawJson) : rawJson;
+
         await peerConnection.setRemoteDescription(offer);
+
         const answer = await peerConnection.createAnswer();
         await peerConnection.setLocalDescription(answer);
 
@@ -241,21 +270,9 @@ async function channelCallJoin(activeCall)
     {
         const offer = await peerConnection.createOffer();
         await peerConnection.setLocalDescription(offer);
-        
+
         await window.HybridWebView.InvokeDotNet("WriteRtcOffer", [JSON.stringify(offer)]);
-        LogMessage(`Joining call with media offer: ${JSON.stringify(offer)}`);
-        
-        localStream.getTracks().forEach(track => {
-            peerConnection.addTrack(track, localStream);
-        });
-        
-        peerConnection.addEventListener('track', event => {
-           LogMessage("Received track: " + event.streams[0]);
-            event.streams[0].getTracks().forEach(track => {
-                LogMessage(`Add a track to the remoteStream: ${track}`);
-                remoteStream.addTrack(track);
-            });
-        });
+        LogMessage("Joining call with media offer: " + JSON.stringify(offer));
     }
 }
 
@@ -263,20 +280,20 @@ async function CSharpCallTest(value)
 {
     LogMessage("Called from C#: " + value);
 }
-async function AnswerCallback(answer)
-{
-    LogMessage("Answer: " + answer);
-    
-    let callBack = JSON.parse(answer);
-    LogMessage("Call Back: " + callBack);
-    
-    if (!peerConnection.currentRemoteDescription && callBack)
-    {
-        LogMessage("Current answer: " + callBack);
-        const desc = new RTCSessionDescription(answer);
-        await peerConnection.setRemoteDescription(desc);
-    }
-}
+//async function AnswerCallback(answer)
+//{
+//    LogMessage("Answer: " + answer);
+//    
+//    let callBack = JSON.parse(answer);
+//    LogMessage("Call Back: " + callBack);
+//    
+//    if (!peerConnection.currentRemoteDescription && callBack)
+//    {
+//        LogMessage("Current answer: " + callBack);
+//        const desc = new RTCSessionDescription(answer);
+//        await peerConnection.setRemoteDescription(desc);
+//    }
+//}
 
 async function CollectIceCandidates()
 {
@@ -284,6 +301,8 @@ async function CollectIceCandidates()
 }
 async function handleRtcSignal(rawJson) {
     try {
+        LogMessage("handleRtcSignal raw: " + JSON.stringify(rawJson));
+
         const msg = typeof rawJson === "string" ? JSON.parse(rawJson) : rawJson;
 
         LogMessage("Received signal: " + msg.type + " from " + msg.from + " in " + msg.channelId);
@@ -436,8 +455,15 @@ async function waitForIceGatheringComplete(pc) {
     });
 }
 
+function dispatchRtcSignal(rawJson) {
+    handleRtcSignal(rawJson);
+    return "ok";
+}
+
 window.handleRtcSignal = handleRtcSignal;
 
+window.dispatchRtcSignal = dispatchRtcSignal;
+
 window.addEventListener("HybridWebViewMessageReceived", function (e) {
     LogMessage("Raw message: " + e.detail.message);
 });
@@ -446,4 +472,9 @@ window.addEventListener("load", async () => {
     LogMessage("RTC page loaded");
     window.HybridWebView.SendRawMessage("rtc_page_ready");
     await loadDevices();
-});
+});
+
+window.dispatchRtcSignal = function(rawJson) {
+    handleRtcSignal(rawJson);
+    return "ok";
+};