I've been using a little matrix app of my own making that sends notificatins to a specific matrix room when big jobs complete. Its nothing fancy (and conceptually not different than slack notifications), and sysadmins have been leveraging email for the same exact purpose...but i like me some matrix...plus, said same matrix room can be made to receive other/outside notifications too; win-win!

How have you been doing that? I'm new to using matrix, is that a builtin functionality or an extension to the client you use?