Got at least one data fetching method working; turns out, we can't use a patched LogicStack to get the data

Vendor/EmbedIO-3.5.2/RequestHandler.cs

@@ -0,0 +1,61 @@
+using System;
+using EmbedIO.Internal;
+
+namespace EmbedIO
+{
+    /// <summary>
+    /// Provides standard request handler callbacks.
+    /// </summary>
+    /// <seealso cref="RequestHandlerCallback"/>
+    public static class RequestHandler
+    {
+        /// <summary>
+        /// <para>Returns an exception object that, when thrown from a module's
+        /// <see cref="IWebModule.HandleRequestAsync">HandleRequestAsync</see> method, will cause the HTTP context
+        /// to be passed down along the module chain, regardless of the value of the module's
+        /// <see cref="IWebModule.IsFinalHandler">IsFinalHandler</see> property.</para>
+        /// </summary>
+        /// <returns>A newly-created <see cref="Exception"/>.</returns>
+        public static Exception PassThrough() => new RequestHandlerPassThroughException();
+
+        /// <summary>
+        /// <para>Returns a <see cref="RequestHandlerCallback" /> that unconditionally sends a <c>401 Unauthorized</c> response.</para>
+        /// </summary>
+        /// <param name="message">A message to include in the response.</param>
+        /// <returns>A <see cref="RequestHandlerCallback" />.</returns>
+        public static RequestHandlerCallback ThrowUnauthorized(string? message = null)
+            => _ => throw HttpException.Unauthorized(message);
+
+        /// <summary>
+        /// <para>Returns a <see cref="RequestHandlerCallback" /> that unconditionally sends a <c>403 Forbidden</c> response.</para>
+        /// </summary>
+        /// <param name="message">A message to include in the response.</param>
+        /// <returns>A <see cref="RequestHandlerCallback" />.</returns>
+        public static RequestHandlerCallback ThrowForbidden(string? message = null)
+            => _ => throw HttpException.Forbidden(message);
+
+        /// <summary>
+        /// <para>Returns a <see cref="RequestHandlerCallback" /> that unconditionally sends a <c>400 Bad Request</c> response.</para>
+        /// </summary>
+        /// <param name="message">A message to include in the response.</param>
+        /// <returns>A <see cref="RequestHandlerCallback" />.</returns>
+        public static RequestHandlerCallback ThrowBadRequest(string? message = null)
+            => _ => throw HttpException.BadRequest(message);
+
+        /// <summary>
+        /// <para>Returns a <see cref="RequestHandlerCallback" /> that unconditionally sends a <c>404 Not Found</c> response.</para>
+        /// </summary>
+        /// <param name="message">A message to include in the response.</param>
+        /// <returns>A <see cref="RequestHandlerCallback" />.</returns>
+        public static RequestHandlerCallback ThrowNotFound(string? message = null)
+            => _ => throw HttpException.NotFound(message);
+
+        /// <summary>
+        /// <para>Returns a <see cref="RequestHandlerCallback" /> that unconditionally sends a <c>405 Method Not Allowed</c> response.</para>
+        /// </summary>
+        /// <param name="message">A message to include in the response.</param>
+        /// <returns>A <see cref="RequestHandlerCallback" />.</returns>
+        public static RequestHandlerCallback ThrowMethodNotAllowed(string? message = null)
+            => _ => throw HttpException.MethodNotAllowed(message);
+    }
+}