<script src="https://cdn.jsdelivr.net/npm/jquery@3.5.1/dist/jquery.min.js"></script>

<link rel="stylesheet" href="https://cdn.jsdelivr.net/gh/fancyapps/fancybox@3.5.7/dist/jquery.fancybox.min.css" />
<script src="https://cdn.jsdelivr.net/gh/fancyapps/fancybox@3.5.7/dist/jquery.fancybox.min.js"></script>

<script type="text/javascript">
	$(document).ready(function() { 
    
    $('a[href*="https://www.youtube.com/watch?"]').each(function() {
  $(this).attr('data-fancybox','');
 });
      
   $('a[href*="https://youtu.be/"]').each(function() {
  $(this).attr('data-fancybox','');
 });    
	
	
	});
</script>

<script>
$(document).ready(function(){
  // Add smooth scrolling to all links
  $("a").on('click', function(event) {

    // Make sure this.hash has a value before overriding default behavior
    if (this.hash !== "") {
      // Prevent default anchor click behavior
      event.preventDefault();

      // Store hash
      var hash = this.hash;

      // Using jQuery's animate() method to add smooth page scroll
      // The optional number (800) specifies the number of milliseconds it takes to scroll to the specified area
      $('html, body').animate({
        scrollTop: $(hash).offset().top
      }, 800, function(){
   
        // Add hash (#) to URL when done scrolling (default click behavior)
        window.location.hash = hash;
      });
    } // End if
  });
});
</script>

Aggiungendo il codice in tutte le pagine non ci sono problemi

il clic si attiva su ID dell’elemento sia un <p> o un <div>