HTML/JS embed source to get a Carrd web page logging scroll depth events to Google Analytics (should work for any website loading GA via https://www.googletagmanager.com/gtag/js?id=UA-XXXXX-X)

carrd_google_analytics_scroll_depth.html

<script>
// TODO: Replace the percentages and names below with those relevant to your website
var percentagesToReport = new Map();
percentagesToReport.set(25, 'Section2');
percentagesToReport.set(50, 'Section3');
percentagesToReport.set(75, 'Section4');
percentagesToReport.set(90, 'Section5');

function reportScroll(scrollLocationName) {
  gtag('event', scrollLocationName, {
    'event_category': 'Scrolling',
    'event_label': '{{Page URL}}',
    'non_interaction': true
  });
}

document.addEventListener('scroll', function() {
  var h =  document.documentElement,
      b =  document.body,
      st =  'scrollTop',
      sh =  'scrollHeight';
 
  var percent = parseInt ( (h[st]||b[st]) / ((h[sh]||b[sh]) - h.clientHeight) * 100);
 
//  console.log(percent + "%"); // Uncomment to debug all scrolling to console
  if (percentagesToReport.has(percent)) {
    var scrollLocationName = percentagesToReport.get(percent);
    console.log("Reporting " + percent + "% scroll (" + scrollLocationName + ") to GA");
    reportScroll('S' + percent + ':' + scrollLocationName);
    percentagesToReport.delete(percent);
  }
});
</script>