How to detected when user stop scrolling with Virtual Scroll - Angular 9

Question

I want to display a message when the user stop scrolling with the Virtual Scroll. I tried the following approach, but the message i want to display never appear when i stop scrolling.

this.scrollDispatcher.scrolled().pipe(
  tap(() => this.scroll = true),
  debounceTime(100))
  .subscribe(event => {
      this.scroll = false;
      console.log('scrolling stopped');
 });

<div style="position: fixed; top: 50%; left: 50%" *ngIf="!scroll">Scrolling stopped</div>

What's wrong with my code ? There's a better working approach ?

Thanks