Same issue here! In the Chrome developer console (accessed by F12 on Windows), an error is raised because the file is served over HTTP.
Mixed Content: The site at 'https://zarkonnen.itch.io/' was loaded over a secure connection, but the file at 'http://www.zarkonnen.com/static/bumble/media/uploads/Airships_1.0.21.1_Windows.zip' was loaded over an insecure connection. This file should be served over HTTPS. This download has been blocked. See https://blog.chromium.org/2020/02/protecting-users-from-insecure.html for more details.
P.S. for anyone trying to download Airships with Chrome, you can click the second link from the message in the developer console to start the download.