There is an actual issue

apps/repl/config/environment.js

@@ -13,10 +13,7 @@ module.exports = function (environment) {
         // Here you can enable experimental features on an ember canary build
         // e.g. EMBER_NATIVE_DECORATOR_SUPPORT: true
       },
-      EXTEND_PROTOTYPES: {
-        // Prevent Ember Data from overriding Date.parse.
-        Date: false,
-      },
+      EXTEND_PROTOTYPES: false,
     },
 
     APP: {

apps/repl/ember-cli-build.js

@@ -37,6 +37,11 @@ module.exports = async function (defaults) {
 
   let app = new EmberApp(defaults, config);
 
+  // Adds:
+  //  - ember-template-compiler
+  //  - @glimmer/syntax
+  // app.import('vendor/ember/ember-template-compiler.js');
+
   const { Webpack } = require('@embroider/webpack');
   const { BundleAnalyzerPlugin } = require('webpack-bundle-analyzer');
 

package.json

@@ -59,6 +59,9 @@
         "rollup",
         "rsvp"
       ]
+    },
+    "patchedDependencies": {
+      "ember-source@5.10.0": "patches/ember-source@5.10.0.patch"
     }
   }
 }

packages/app-support/limber-ui/addon/package.json

@@ -96,15 +96,8 @@
     "prettier-plugin-ember-template-tag": "2.0.2",
     "rollup": "^4.17.2",
     "rollup-plugin-copy": "^3.5.0",
-<<<<<<< HEAD
-    "typescript": "^5.4.5",
-    "webpack": "5.92.0"
-||||||| parent of cbeaa507 (ember-source *really* needs to drop the peer on webpack)
-    "typescript": "^5.4.5"
-=======
     "typescript": "^5.4.5",
     "webpack": "^5.92.1"
->>>>>>> cbeaa507 (ember-source *really* needs to drop the peer on webpack)
   },
   "publishConfig": {
     "registry": "https://registry.npmjs.org"

packages/ember-repl/addon/src/compile/formats/gjs/index.ts

@@ -87,6 +87,8 @@ async function preprocess(input: string, name: string): Promise<string> {
   return processor.process(input, `${name}.js`);
 }
 
+console.log(compiler);
+
 async function transform(
   intermediate: string,
   name: string,

patches/ember-source@5.10.0.patch

@@ -0,0 +1,34 @@
+diff --git a/dist/ember-template-compiler.js b/dist/ember-template-compiler.js
+index 6b97705af339ca7eef12ed2a5b6ebf587c3bdc50..36a2e115d193fe82ef0802394664058abfb2ef99 100644
+--- a/dist/ember-template-compiler.js
++++ b/dist/ember-template-compiler.js
+@@ -18734,29 +18734,6 @@ var define, require;
+                     default: bootstrap
+           }, Symbol.toStringTag, { value: 'Module' });
+
+-          // Globals mode template compiler
+-          if (emberApp__namespace.default) {
+-            let Application = emberApp__namespace.default;
+-            let {
+-              hasTemplate,
+-              setTemplate
+-            } = emberGlimmer__namespace;
+-            let {
+-              hasDOM
+-            } = emberinternalsBrowserEnvironmentIndex;
+-            Application.initializer({
+-              name: 'domTemplates',
+-              initialize() {
+-                if (hasDOM) {
+-                  bootstrap({
+-                    context: document,
+-                    hasTemplate,
+-                    setTemplate
+-                  });
+-                }
+-              }
+-            });
+-          }
+
+           const emberTemplateCompilerLibSystemInitializer = /*#__PURE__*/Object.defineProperty({
+                     __proto__: null