That was my first exposure to webhooks was slack, I see it in a few places now that triangle circle-corner logo.

I don't know how often the front page of Hacker news is updated but you could build this yourself.

CRON > PHP > CURL > HTMLDOMScraper > Slack webhook

I had everything else except the CRON part, I had trouble trying to run that.

note: the CRON thing for me, I tried Ubuntu and Debian, I don't know I couldn't get it to work. I couldn't get a simple php script to execute on the timed interval.

So a dumb solution would be to use a setTimeout poll with JavaScript and call the AJAX request to the PHP script which then runs everything else.