After it was previewed in an announcement last April, Facebook is now rolling out the Messenger app for Mac through the App Store. It was originally planned to come to macOS by December 2019, but is now rolling out in selected regions.
The app has been seen in the Mac App Store for France so far, with other regions likely receiving the update over the course of this month. Facebook may be publicly testing it and doesn’t want it worldwide just yet – but that’s an odd way of testing an app for bugs.
Messenger for Mac isn’t built on Apple’s Catalyst but rather Electron. This will allow for compatibility with older versions of macOS that aren’t designed to support Project Catalyst.