Bootstrap JS not loading in Symfony 5 with Encore

I am having difficulties loading Bootstrap's js with Symfony 5, encore, stimulus etc...

jquery, popper, corejs, etc all installed and at least jquery is working...

app.scss and app.js seems to compile well using sass, postcss and babel, including Bootstrap's CSS. Just Bootstrap's JS is not there, so no dropdowns, etc.

assets/app.js

// any CSS you import will output into a single css file (app.css in this case)
import './styles/app.scss';

// start the Stimulus application
import './bootstrap';

assets/bootstrap,js

import { startStimulusApp } from '@symfony/stimulus-bridge';

// Registers Stimulus controllers from controllers.json and in the controllers/ directory
 export const app = startStimulusApp(require.context(
    '@symfony/stimulus-bridge/lazy-controller-loader!./controllers',
    true,
    /\.(j|t)sx?$/
));

// register any custom, 3rd party controllers here
// app.register('some_controller_name', SomeImportedController);

note: There is no specific controller under assets/controllers

webpack.config.js

const Encore = require('@symfony/webpack-encore');

// Manually configure the runtime environment if not already configured yet by the "encore" command.
// It's useful when you use tools that rely on webpack.config.js file.
if (!Encore.isRuntimeEnvironmentConfigured()) {
    Encore.configureRuntimeEnvironment(process.env.NODE_ENV || 'dev');
}

Encore
  // directory where compiled assets will be stored
  .setOutputPath("public/build/")
  // public path used by the web server to access the output path
  .setPublicPath("/build")
  // only needed for CDN's or sub-directory deploy
  //.setManifestKeyPrefix('build/')

  /*
   * ENTRY CONFIG
   *
   * Each entry will result in one JavaScript file (e.g. app.js)
   * and one CSS file (e.g. app.css) if your JavaScript imports CSS.
   */
  .addEntry("app", "./assets/app.js")

  // enables the Symfony UX Stimulus bridge (used in assets/bootstrap.js)
  .enableStimulusBridge('./assets/controllers.json')

  // When enabled, Webpack "splits" your files into smaller pieces for greater optimization.
  .splitEntryChunks()

  // will require an extra script tag for runtime.js
  // but, you probably want this, unless you're building a single-page app
  .enableSingleRuntimeChunk()

  /*
   * FEATURE CONFIG
   *
   * Enable & configure other features below. For a full
   * list of features, see:
   * https://symfony.com/doc/current/frontend.html#adding-more-features
   */
  .cleanupOutputBeforeBuild()
  .enableBuildNotifications()
  .enableSourceMaps(!Encore.isProduction())
  // enables hashed filenames (e.g. app.abc123.css)
  .enableVersioning(Encore.isProduction())

  .configureBabel((config) => {
    config.plugins.push("@babel/plugin-proposal-class-properties");
  })

  // enables @babel/preset-env polyfills
  .configureBabelPresetEnv((config) => {
    config.useBuiltIns = "usage";
    config.corejs = 3;
  })

  // enables Sass/SCSS support
  .enableSassLoader()

  // enable PostCSS
  .enablePostCssLoader();

// uncomment if you use TypeScript
//.enableTypeScriptLoader()

// uncomment if you use React
//.enableReactPreset()

// uncomment to get integrity="..." attributes on your script & link tags
// requires WebpackEncoreBundle 1.4 or higher
//.enableIntegrityHashes(Encore.isProduction())

// uncomment if you're having problems with a jQuery plugin
// .autoProvidejQuery()

module.exports = Encore.getWebpackConfig();

package.json (only dependencies)

  "devDependencies": {
    "@popperjs/core": "^2.10.2",
    "@symfony/stimulus-bridge": "^2.1.0",
    "@symfony/webpack-encore": "^1.6.1",
    "autoprefixer": "^10.4.0",
    "bootstrap": "^5.1.3",
    "core-js": "^3.19.1",
    "jquery": "^3.6.0",
    "postcss-loader": "^6.2.0",
    "sass": "^1.43.4",
    "sass-loader": "^12.3.0",
    "stimulus": "^2.0.0",
    "webpack-notifier": "^1.14.1"
  },
  "dependencies": {
    "popper.js": "^1.16.1"
  }

How to troubleshoot further?