If you pay for it, touring plans will send you a notification if an adr time you're looking for opens up.
Other than that there's no notifications I've ever heard of. No notifications for new FP's, hours changing, etc.
If there is a change in a FP you have, like if the ride goes down, you'll get an email about it and it'll result in an anytime FP. That might be the alerts you're seeing people mention