It’s not really off-topic, because you could use a smart playlist to do that.
But I ask @bitteronthefruit : which client type are you using?
Because all the clients I use have this hub on their main page where you can see new episodes of shows you have watched in the past, called On Deck.
And then there is the hub called ‘Recently added TV Shows’.
And then there is the Plex feature which adds a show into On Deck if a new season has begun – even if you haven’t watched the show for several months.
If you are after a real ‘Alert’, you could take a look at Tautulli and its Notification/Mailing features.
