webpacker: "Uncaught TypeError: root is undefined" when importing from package

I am a bit heavily lost in the quest for a solution to my problem, so apologies if this is not the right place for my question. It appeared the least wrong one to start with and I happily take recommendations where to go with it otherwise.

I want to setup pdf.js in our Rails app and followed the recommendation for webpack users which basically says to simply use import pdfjsLib from 'pdfjs-dist/webpack'; which takes care of setting up the worker. With this code in my JavaScript I get the following error in my browser console when I access a page that triggers this code:

Uncaught TypeError: root is undefined
    webpackUniversalModuleDefinition pdf.js:77
    js                               pdf.js:78

I cannot find the respective code in the pdf.js repository, I assume it is generated by some build/release pipeline. But here is what the respective file in node_modules/pdfjs-dist/build/pdf.js looks like. It starts with something that appears to me like something webpack specific:

(function webpackUniversalModuleDefinition(root, factory) {
	if(typeof exports === 'object' && typeof module === 'object')
		module.exports = factory();
	else if(typeof define === 'function' && define.amd)
		define("pdfjs-dist/build/pdf", [], factory);
	else if(typeof exports === 'object')
		exports["pdfjs-dist/build/pdf"] = factory();
	else
		root["pdfjs-dist/build/pdf"] = root.pdfjsLib = factory();
})(this, function() {
// all the code
});

The flagged lines belong to the body of a function defined like this:

// define __esModule on exports
__w_pdfjs_require__.r = function(exports) {
  if(typeof Symbol !== 'undefined' && Symbol.toStringTag) {                  // <-- Line 77
    Object.defineProperty(exports, Symbol.toStringTag, { value: 'Module' }); // <-- Line 78
  }
  Object.defineProperty(exports, '__esModule', { value: true });
};

A gist with the complete pdf.js from the pdfjs-dist package can be viewed here

That is my situation and I am lost between webpacker, webpack and pdf.js. My intuition was that I probably need to tell webpack(er?) that it should inject something for the root value. However, this is a formal parameter of the module definition as far as I see it. So what value for what keyword would I have to inject exactly and where? I was down to the imports-loader for webpack but either did not figure out how to correctly embed its rules in the webpack config in config/webpack/environment.js. I try & only-errored for some time and gave up.

On the other hand I think/hope/assume that it should be possible to somehow only do what the README for pdf.js says: Import the thing via webpack.js. After all it is advertised as the zero-configuration method for Webpack users and I would like to be one of that happy users. Maybe I am only missing something very simple that is painfully obvious if you know it … but I just don’t know and couldn’t figure out in three days so far. So, anyone a hint or maybe even the solution? 😃