Client side events

[nerdoc]

Do the client side events occur when a Stream changes the DOM?
I have a Stream adding a Bootstrap toast as push notification message to a user that works reasonably well - But I can either show the Toast directly by attribute (class show) - then it is never faded, and the user has to remove it by click on the close button.
Or, what I really want, is keep it hidden, and call bootstrap's javascript to show it, which starts a counter, and removes it again after a period of time.

But therefore I need to respond to a Js event like turbo:frame:load. According to this discussion, this event is not triggered if the HTML comes from a Stream.

        document.documentElement.addEventListener("turbo:frame-load", evt => {
          console.log("A new TurboFrame appeared:", evt.target);
      })

Is there anything I can do to trigger a client side event when a Stream's HTML comes in?
I saw that turbo-django.js has defined some events - but I am not Js-smart enough to understand that code properly.