You don’t know what website they get sent to, you only get given a source ID which you can whitelist or blacklist. I only really know some native sources that give you the websites url, most don’t though. I think in the future they will change it as it’s an outdated format IMO.Then I'd look in the list for tennis websites OR URL's that include the word "tennis" (that I'd prescreen)
Perhaps the registered users for push notifications