Facebook is is working on a new official app for Windows 10 desktop. The app is in private beta, and has seen a number of updates already.
It is free to download, but most users are not able to log in.
Now the WC reports that the app is now accepting some new users again. It seems to be a bit of the luck of the draw, and it certainly did not let me log in.
See screen shots of the app below.
Try your luck with the app in the Windows Store here.