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/HttpNotAcceptableException.cs

@@ -0,0 +1,55 @@
+using System.Net;
+
+namespace EmbedIO
+{
+    /// <summary>
+    /// When thrown, breaks the request handling control flow
+    /// and sends a redirection response to the client.
+    /// </summary>
+#pragma warning disable CA1032 // Implement standard exception constructors - they have no meaning here.
+    public class HttpNotAcceptableException : HttpException
+#pragma warning restore CA1032
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="HttpNotAcceptableException"/> class,
+        /// without specifying a value for the response's <c>Vary</c> header.
+        /// </summary>
+        public HttpNotAcceptableException()
+            : this(null)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="HttpNotAcceptableException"/> class.
+        /// </summary>
+        /// <param name="vary">
+        /// <para>A value, or a comma-separated list of values, to set the response's <c>Vary</c> header to.</para>
+        /// <para>Although not specified in <see href="https://tools.ietf.org/html/rfc7231#section-6.5.6">RFC7231</see>,
+        /// this may help the client to understand why the request has been rejected.</para>
+        /// <para>If this parameter is <see langword="null"/> or the empty string, the response's <c>Vary</c> header
+        /// is not set.</para>
+        /// </param>
+        public HttpNotAcceptableException(string? vary)
+            : base((int)HttpStatusCode.NotAcceptable)
+        {
+            Vary = string.IsNullOrEmpty(vary) ? null : vary;
+        }
+
+        /// <summary>
+        /// Gets the value, or comma-separated list of values, to be set
+        /// on the response's <c>Vary</c> header.
+        /// </summary>
+        /// <remarks>
+        /// <para>If the empty string has been passed to the <see cref="HttpNotAcceptableException(string)"/>
+        /// constructor, the value of this property is <see langword="null"/>.</para>
+        /// </remarks>
+        public string? Vary { get; }
+
+        /// <inheritdoc />
+        public override void PrepareResponse(IHttpContext context)
+        {
+            if (Vary != null)
+                context.Response.Headers.Add(HttpHeaderNames.Vary, Vary);
+        }
+    }
+}