try skypack -> esm.run (it bundles everything into one file)

frontend/app.js

@@ -1,4 +1,4 @@
-import RFB from "https://cdn.skypack.dev/pin/@novnc/novnc@v1.3.0-RRNSIy674lWHJVNg8Apd/mode=imports,min/unoptimized/core/rfb.js";
+import RFB from "https://cdn.jsdelivr.net/npm/@novnc/novnc/core/rfb.js/+esm";
 
 // DOS-style box for text
 const cmd = document.getElementById("cmd-text");
@@ -12,7 +12,7 @@ if (window.WebSocket) {
     document.getElementById("display"),
     "wss://spin-vm.jrvs.io",
     {
-      wsProtocols: ["binary", "base64"],
+      wsProtocols: ["binary", "base64"]
     }
   );
   rfb.addEventListener("connect", () => {