Hearthstone Deck Tracker (HDT) must run in the same Wine prefix and sandbox as Hearthstone to detect the game. Faugus Launcher isolates each game entry in its own bubblewrap sandbox with its own wineserver, so adding HDT as a separate entry won't work — even if both entries point to the same prefix.

The solution is to use Faugus's Add App feature to launch HDT alongside Battle.net in a single sandbox.