Angular Universal doesn't take over rendering on client

I am currently trying to add Server Side Rendering (SSR) to my angular app following the official angular guide for angular universal. I was able to set up the express server and the response I get from the server contains my app, although looking a bit quirky as if some CSS was missing resulting in FontAwesome icons being rendered too big, etc.

For some reason though, the client/browser never takes over (re)rendering and the website stays the same as it came as response from the server. It is not interactive and completely static. When clicking controls (except for links) or interactive elements, nothing happens.

Here you can see parts of the App Shell / HTML.

Here is the Network Traffic.

The package.json:

    {
      "name": "my-app",
      "version": "0.0.0",
      "scripts": {
        "ng": "ng",
        "start": "ng serve",
        "build": "ng build",
        "test": "ng test",
        "lint": "ng lint",
        "e2e": "ng e2e",
        "dev:ssr": "ng run my-app:serve-ssr",
        "serve:ssr": "node dist/my-app/server/main.js",
        "build:ssr": "ng build --prod && ng run my-app:server:production",
        "prerender": "ng run my-app:prerender"
      },
      "private": true,
      "dependencies": {
        "@agm/core": "^1.1.0",
        "@angular/animations": "^10.0.14",
        "@angular/common": "^10.0.14",
        "@angular/compiler": "^10.0.14",
        "@angular/core": "^10.0.14",
        "@angular/elements": "^10.0.14",
        "@angular/forms": "^10.0.14",
        "@angular/localize": "~10.0.14",
        "@angular/platform-browser": "^10.0.14",
        "@angular/platform-browser-dynamic": "^10.0.14",
        "@angular/platform-server": "^10.0.14",
        "@angular/router": "^10.0.14",
        "@angular/service-worker": "^10.0.14",
        "@fortawesome/angular-fontawesome": "^0.7.0",
        "@fortawesome/fontawesome-svg-core": "^1.2.30",
        "@fortawesome/free-brands-svg-icons": "^5.14.0",
        "@fortawesome/free-regular-svg-icons": "^5.14.0",
        "@fortawesome/free-solid-svg-icons": "^5.14.0",
        "@ng-bootstrap/ng-bootstrap": "^7.0.0",
        "@ng-select/ng-select": "^4.0.4",
        "@nguniversal/express-engine": "^10.0.2",
        "@webcomponents/webcomponentsjs": "^2.2.10",
        "bootstrap": "^4.3.1",
        "bufferutil": "^4.0.1",
        "core-js": "^2.5.4",
        "document-register-element": "^1.13.2",
        "domino": "^2.1.6",
        "express": "^4.15.2",
        "html-webpack-plugin": "^2.30.1",
        "intersection-observer": "^0.7.0",
        "jquery": "^3.5.1",
        "ng-lazyload-image": "^5.1.2",
        "ng5-slider": "^1.1.14",
        "ngx-cookie-service": "^2.2.0",
        "ngx-infinite-scroll": "^7.1.0",
        "popper.js": "^1.14.7",
        "rxjs": "^6.6.2",
        "tslib": "^2.0.0",
        "utf-8-validate": "^5.0.2",
        "webpack": "^4.44.1",
        "xmlhttprequest": "^1.8.0",
        "zone.js": "~0.10.2"
      },
      "devDependencies": {
        "@angular-devkit/build-angular": "~0.1000.8",
        "@angular/cli": "^10.0.8",
        "@angular/compiler-cli": "^10.0.14",
        "@angular/language-service": "^10.0.14",
        "@nguniversal/builders": "^10.0.2",
        "@types/express": "^4.17.0",
        "@types/jasmine": "~2.8.8",
        "@types/jasminewd2": "~2.0.3",
        "@types/node": "^12.11.1",
        "codelyzer": "^6.0.0",
        "jasmine-core": "~3.5.0",
        "jasmine-spec-reporter": "~5.0.0",
        "karma": "~5.0.0",
        "karma-chrome-launcher": "~3.1.0",
        "karma-coverage-istanbul-reporter": "~3.0.2",
        "karma-jasmine": "~3.3.0",
        "karma-jasmine-html-reporter": "^1.5.0",
        "ngx-perfect-scrollbar": "^7.2.1",
        "node-sass": "^4.14.1",
        "protractor": "~7.0.0",
        "ts-node": "~7.0.0",
        "tslint": "~6.1.0",
        "typescript": "^3.9.7"
      }
    }

The angular.json:

{
  "$schema": "./node_modules/@angular/cli/lib/config/schema.json",
  "version": 1,
  "newProjectRoot": "projects",
  "projects": {
    "my-app": {
      "i18n": {
        "locales": {
          "de-AT": {
            "translation": "src/locale/messages.de-AT.xlf",
            "baseHref": ""
          }
        }
      },
      "root": "",
      "sourceRoot": "src",
      "projectType": "application",
      "prefix": "app",
      "schematics": {
        "@schematics/angular:component": {
          "style": "scss"
        }
      },
      "architect": {
        "build": {
          "builder": "@angular-devkit/build-angular:browser",
          "options": {
            "watch": false,
            "index": "src/index.html",
            "outputPath": "dist/my-app/browser",
            "main": "src/main.ts",
            "polyfills": "src/polyfills.ts",
            "tsConfig": "src/tsconfig.app.json",
            "assets": [
              "src/favicon.ico",
              "src/apple-touch-icon.png",
              "src/apple-touch-icon-precomposed.png",
              "src/robots.txt",
              "src/sitemap.xml",
              "src/assets",
              "src/manifest.json"
            ],
            "styles": [
              "src/styles.scss"
            ],
            "scripts": [
              {
                "input": "node_modules/document-register-element/build/document-register-element.js"
              }
            ]
          },
          "configurations": {
            "production": {
              "fileReplacements": [
                {
                  "replace": "src/environments/environment.ts",
                  "with": "src/environments/environment.prod.ts"
                }
              ],
              "i18nMissingTranslation": "error",
              "localize": [
                "de-AT"
              ],
              "optimization": true,
              "outputHashing": "bundles",
              "sourceMap": false,
              "extractCss": true,
              "namedChunks": false,
              "aot": true,
              "extractLicenses": true,
              "vendorChunk": false,
              "buildOptimizer": true,
              "budgets": [
                {
                  "type": "initial",
                  "maximumWarning": "2mb",
                  "maximumError": "3mb"
                },
                {
                  "type": "anyComponentStyle",
                  "maximumWarning": "20kb"
                }
              ],
              "serviceWorker": true,
              "ngswConfigPath": "src/ngsw-config.json"
            },
            "dev": {
              "fileReplacements": [
                {
                  "replace": "src/environments/environment.ts",
                  "with": "src/environments/environment.dev.ts"
                }
              ],
              "aot": false,
              "i18nMissingTranslation": "error",
              "localize": [
                "de-AT"
              ],
              "optimization": false,
              "outputHashing": "none",
              "extractCss": true,
              "namedChunks": true,
              "extractLicenses": true,
              "vendorChunk": false,
              "budgets": [
                {
                  "type": "initial",
                  "maximumWarning": "10mb",
                  "maximumError": "12mb"
                },
                {
                  "type": "anyComponentStyle",
                  "maximumWarning": "20kb"
                }
              ],
            }
          }
        },
        "serve": {
          "builder": "@angular-devkit/build-angular:dev-server",
          "options": {
            "browserTarget": "my-app:build"
          },
          "configurations": {
            "production": {
              "browserTarget": "my-app:build:production"
            }
          }
        },
        "extract-i18n": {
          "builder": "@angular-devkit/build-angular:extract-i18n",
          "options": {
            "browserTarget": "my-app:build"
          }
        },
        "test": {
          "builder": "@angular-devkit/build-angular:karma",
          "options": {
            "main": "src/test.ts",
            "polyfills": "src/polyfills.ts",
            "tsConfig": "src/tsconfig.spec.json",
            "karmaConfig": "src/karma.conf.js",
            "styles": [
              "src/styles.scss"
            ],
            "scripts": [],
            "assets": [
              "src/favicon.ico",
              "src/robots.txt",
              "src/sitemap.xml",
              "src/assets",
              "src/manifest.json"
            ]
          }
        },
        "lint": {
          "builder": "@angular-devkit/build-angular:tslint",
          "options": {
            "tsConfig": [
              "src/tsconfig.app.json",
              "src/tsconfig.spec.json",
              "src/tsconfig.server.json"
            ],
            "exclude": [
              "**/node_modules/**"
            ]
          }
        },
        "server": {
          "builder": "@angular-devkit/build-angular:server",
          "options": {
            "outputPath": "dist/my-app/server",
            "main": "server.ts",
            "tsConfig": "src/tsconfig.server.json"
          },
          "configurations": {
            "production": {
              "fileReplacements": [
                {
                  "replace": "src/environments/environment.ts",
                  "with": "src/environments/environment.prod.ts"
                }
              ],
              "sourceMap": false,
              "optimization": true
            }
          }
        },
        "serve-ssr": {
          "builder": "@nguniversal/builders:ssr-dev-server",
          "options": {
            "browserTarget": "my-app:build",
            "serverTarget": "my-app:server"
          },
          "configurations": {
            "production": {
              "browserTarget": "my-app:build:production",
              "serverTarget": "my-app:server:production"
            }
          }
        },
        "prerender": {
          "builder": "@nguniversal/builders:prerender",
          "options": {
            "browserTarget": "my-app:build:production",
            "serverTarget": "my-app:server:production",
            "routes": [
              "/"
            ]
          },
          "configurations": {
            "production": {}
          }
        }
      }
    },
    "my-app-e2e": {
      "root": "e2e/",
      "projectType": "application",
      "prefix": "",
      "architect": {
        "e2e": {
          "builder": "@angular-devkit/build-angular:protractor",
          "options": {
            "protractorConfig": "e2e/protractor.conf.js",
            "devServerTarget": "my-app:serve"
          },
          "configurations": {
            "production": {
              "devServerTarget": "my-app:serve:production"
            }
          }
        },
        "lint": {
          "builder": "@angular-devkit/build-angular:tslint",
          "options": {
            "tsConfig": "e2e/tsconfig.e2e.json",
            "exclude": [
              "**/node_modules/**"
            ]
          }
        }
      }
    }
  },
  "defaultProject": "my-app"
}

The server.ts:

import 'zone.js/dist/zone-node';

import { ngExpressEngine } from '@nguniversal/express-engine';
import * as express from 'express';
import { join } from 'path';

const domino = require('domino');
const fs = require('fs');
const path = require('path');

const template = fs
  .readFileSync(path.join('dist/my-app/browser/de-AT', 'index.html'))
  .toString();
const window = domino.createWindow(template);

// Ignite UI browser objects abstractions
(global as any).window = window;
(global as any).document = window.document;
(global as any).Event = window.Event;
(global as any).KeyboardEvent = window.KeyboardEvent;
(global as any).MouseEvent = window.MouseEvent;
(global as any).FocusEvent = window.FocusEvent;
(global as any).PointerEvent = window.PointerEvent;
(global as any).HTMLElement = window.HTMLElement;
(global as any).HTMLElement.prototype.getBoundingClientRect = () => {
    return {
      left: '',
      right: '',
      top: '',
      bottom: ''
  };
};

(global as any).XMLHttpRequest = require('xmlhttprequest').XMLHttpRequest;

// Other optional depending on your application configuration
(global as any).object = window.object;
(global as any).navigator = window.navigator;
(global as any).localStorage = window.localStorage;
(global as any).DOMTokenList = window.DOMTokenList;

Object.defineProperty(window.document.body.style, 'transform', {
  value: () => {
    return {
      enumerable: true,
      configurable: true,
    };
  },
});
(global as any).CSS = null;
(global as any).Prism = null;

import { AppServerModule } from './src/main.server';
import { APP_BASE_HREF } from '@angular/common';
import { existsSync } from 'fs';

// The Express app is exported so that it can be used by serverless Functions.
export function app(): express.Express {
  const server = express();
  const distFolder = join(process.cwd(), 'dist/my-app/browser/de-AT');
  const indexHtml = existsSync(join(distFolder, 'index.original.html')) ? 'index.original.html' : 'index';

  // Our Universal express-engine (found @ https://github.com/angular/universal/tree/master/modules/express-engine)
  server.engine('html', ngExpressEngine({
    bootstrap: AppServerModule,
  }));

  server.set('view engine', 'html');
  server.set('views', distFolder);

  // Example Express Rest API endpoints
  // server.get('/api/**', (req, res) => { });
  // Serve static files from /browser
  server.get('*.*', express.static(distFolder, {
    maxAge: '1y'
  }));

  // All regular routes use the Universal engine
  server.get('*', (req, res) => {
    res.render(indexHtml, { req, providers: [{ provide: APP_BASE_HREF, useValue: req.baseUrl }] });
  });

  return server;
}

function run(): void {
  const port = process.env.PORT || 4000;

  // Start up the Node server
  const server = app();
  server.listen(port, () => {
    console.log(`Node Express server listening on http://localhost:${port}`);
  });
}

// Webpack will replace 'require' with '__webpack_require__'
// '__non_webpack_require__' is a proxy to Node 'require'
// The below code is to ensure that the server is run only when not requiring the bundle.
declare const __non_webpack_require__: NodeRequire;
const mainModule = __non_webpack_require__.main;
const moduleFilename = mainModule && mainModule.filename || '';
if (moduleFilename === __filename || moduleFilename.includes('iisnode')) {
  run();
}

export * from './src/main.server';

The tsconfig.base.json:

{
  "compileOnSave": false,
  "compilerOptions": {
    "baseUrl": "./",
    "outDir": "./dist/out-tsc",
    "sourceMap": true,
    "declaration": false,
    "module": "es2020",
    "moduleResolution": "node",
    "emitDecoratorMetadata": true,
    "experimentalDecorators": true,
    "importHelpers": true,
    "target": "es2015",
    "downlevelIteration": true,
    "typeRoots": [
      "node_modules/@types",
      "typings.d.ts"
    ],
    "lib": [
      "es2018",
      "dom"
    ]
  }
}

The tsconfig.server.json:

{
  "extends": "./tsconfig.app.json",
  "compilerOptions": {
    "outDir": "../out-tsc/server",
    "target": "es2016",
    "types": [
      "node"
    ]
  },
  "files": [
    "main.server.ts",
    "../server.ts"
  ],
  "angularCompilerOptions": {
    "entryModule": "./app/app.server.module#AppServerModule"
  }
}

The app.server.module.ts:

    import { NgModule } from '@angular/core';
    import { ServerModule } from '@angular/platform-server';
    import { HttpClientModule, HTTP_INTERCEPTORS } from '@angular/common/http';
    import { UniversalInterceptor } from './universal-interceptor';
    import { AppModule } from './app.module';
    import { AppComponent } from './app.component';

    @NgModule({
      imports: [
        AppModule,
        ServerModule
      ],
      providers: [
        {
          provide: HTTP_INTERCEPTORS,
          useClass: UniversalInterceptor,
          multi: true
        }
      ],
      bootstrap: [AppComponent]
    })
    export class AppServerModule {}

I really don't know what I am doing wrong. Any ideas?