Protractor: Error while waiting for Protractor to sync with the page: "both angularJS testability and angular testability are undefined

You got this error because Protractor by default wait angular page is loaded. If you work with non angular you should add await browser.waitForAngularEnabled(false); to onPrepare block:

 onPrepare: async () => {
 ...
 await browser.waitForAngularEnabled(false);
 ...  

How does this "waiting" mechanism works? I will copy description from code:

     * If set to false, Protractor will not wait for Angular $http and $timeout
     * tasks to complete before interacting with the browser. This can cause
     * flaky tests, but should be used if, for instance, your app continuously
     * polls an API with $timeout.

So, as you can see it is all about $http and $timeout tasks. A bit often developers use it in a not proper way.

In conclusion, if you see such error:

both angularJS testability and angular testability are undefined

you have to add await browser.waitForAngularEnabled(false);.