had a similar issue. I believe Google-Bot do not support modern JS. I simply activated all shims recommended by angular.io see https://angular.io/docs/ts/latest/guide/browser-support.html and added in the script header:

<script src="https://cdnjs.cloudflare.com/ajax/libs/core-js/2.4.1/shim.min.js">
</script>

If you really need all of them I'm not sure, but I need support for older IE anyway.

If this works for all Searchbots is very unclear, if you have to support them you can try https://prerender.io/. However they are also just able to render it with the shims

Hope this helps.

First this was talked about at NG-Conf 2018 Apr For the slides click here

Looking at the source code of the Angular.io here is how the angular guys do this according to the slides

 <script>
    if (window.document.documentMode) {
      // polyfill IE11 in a blocking way
      var s = document.createElement('script');
      s.src = 'generated/ie-polyfills.min.js';
      document.head.appendChild(s);
    } else if (!Object.assign) {
      // polyfill other non-evergreen browsers in a blocking way
      var polyfillUrl = "https://cdn.polyfill.io/v2/polyfill.min.js?features=default,Array.prototype.find&flags=gated&unknown=polyfill";
      // send a blocking XHR to fetch the polyfill
      // then append it to the document so that its eval-ed synchronously
      // this is required because the method used for IE is not reliable with other non-evergreen browsers
      var xhr = new XMLHttpRequest();
      xhr.addEventListener("load", function() {
        var s = document.createElement('script');
        s.type = 'text/javascript';
        var code = this.responseText;
        s.appendChild(document.createTextNode(code));
        document.head.appendChild(s);
      });
      xhr.open("GET", polyfillUrl, false);
      xhr.send();
    }
  </script>

Add the above script in the HEAD section of your index file.

Worth to mention that if you go with the answer of just adding a CDN you most probably are loading a script that is not needed for most of the modern browsers to those browsers as well and should be avoided.

Since your frontend isn't being served by any server side language, I'd recommend using Angular2-Universal to serve a static HTML site on initial load.

You can checkout their quickstart guide and get it working pretty fast.