Angular 15 Universal + Internationalization (localize)

angular.json

{
  "i18n": {
        "sourceLocale": {
          "code": "en",
          "baseHref": "/en/"
        },
        "locales": {
          "es": {
            "translation": "src/locales/messages.es.xlf",
            "baseHref": "/es/"
          },
          "fr": {
            "translation": "src/locales/messages.fr.xlf",
            "baseHref": "/fr/"
          },
          "ht": {
            "translation": "src/locales/messages.ht.xlf",
            "baseHref": "/ht/"
          }
        }
      }
}

server.ts

import "zone.js/node";
import {ngExpressEngine} from "@nguniversal/express-engine";
import * as express      from "express";
import {existsSync}      from "fs";
import {join}            from "path";

import {AppServerModule} from "./src/main.server";
import {environment}     from "./src/environments/environment";
import {LOCALE_ID}       from "@angular/core";
import {APP_BASE_HREF}   from "@angular/common";

// The Express app is exported so that it can be used by serverless Functions.
export function app(): express.Express {
  const server = express();
  const browser = environment.production ? "browser" : "dist/my-site/browser";
  const distFolder = join(process.cwd(), browser);

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

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

  server.get("/", function(req, res) {
    res.redirect("/en");
  });

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

  // All regular routes use the Universal engine
  server.get(
    [
      "/:language(en|fr|es|ht)",
      "/:language(en|fr|es|ht)/*",
    ],
    (req, res) => {
      const lang = req.params["language"];

      const indexHtml = existsSync(
        join(
          `${lang}/${distFolder}`, "index.original.html",
        ),
      ) ? "index.original.html" : "index";

      res.render(`${lang}/${indexHtml}`,
        {
          req,
          providers: [
            {provide: LOCALE_ID, useValue: lang},
            {provide: APP_BASE_HREF, useValue: `/${lang}/`},
          ],
        },
      );
    },
  );

  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";