Age of Empires II DE Game Notifier keeps track of all currently available AoE 2 DE lobbies and players and notifies the user whenever it spots a lobby or a player that the user is interested in.
The program allows you to create a set of rules, based on which you will be getting your notifications. For instance, if you are a Forest Nothing player and you want to play whenever someone from your clan joins a forest nothing game, you can create a set of rules that will tell the program to keep an eye for lobbies that contain keywords "forest" and "nothing" (or just "nothing") and have players whose names contain certain sequences of letters, for example "[B]".

The compiled program can be downloaded from here: https://thismagical.world/aoe-notifier/