The desktop app is part of Pro. You can still download and install it - it'll ask you to sign in and upgrade the moment it opens. See Pro plans, or sign in if you already have Pro.

Windows

Unsigned for now, so Windows will show a "Windows protected your PC" warning - click More info, then Run anyway. This is expected; it is not a sign anything is wrong.

Mac and Linux builds exist too, but they're unsigned and not yet confirmed to actually run on those platforms - for testing only, not a recommended install. See all files on GitHub.