The app is built using Electron, a tool for developing apps for the desktop from a web app, instead of Catalyst. It's not clear for now when the app will be available in the Mac App Store in the U.S. The app has been spotted on the Mac App Store in France, courtesy of MacGeneration. Although a tad late, Messenger for macOS appears to be just rolling out now to users in some territories including France, Australia, Mexico, and Poland (via 9to5Mac). Facebook revealed during its F8 developer conference last year that it was planning to bring a new dedicated Messenger app to macOS and Windows in the fall of 2019.
