On the website, I successfully use the ASHX handler to download files from the server to visitors to my site.
The client suggested not relying on the browser user interface to visualize the download progress, but instead provided some progress on the page to provide a more visual hint.
those. firstly, the user sees the download page with a link / button:

Then, when you click the button Download your file now!, the following should appear:

Unfortunately, even after searching Google and SO for several hours, I found zero similar topics. All cases are related to download, not download. Either I'm using the wrong keywords, or there are no solutions.
So my question is:
(How) could such a loading process be provided?