Hi! I am having the same issue. I downloaded The Unarchiver, but I'm still having issues. On the download page, when I right-click, I do not have an option to "Open With" (maybe because it shows up as a button?). I have the option to copy link, share, inspect element, and services. If I click the link and then pause the download in Finder, and then to try open that with The Unarchiver, I get a message saying the contents cannot be extracted with The Unarchiver (perhaps because it is now a .zip.download?). I also tried downloading in the itch app, and that also did not work. Thanks for any help! I look forward to being able to play. :)
You should be able to select The Unarchiver to extract the files once you fully download the .zip from your game page (not pausing the download) by right-clicking the "Catlateral Damage v1.0.8 Mac 64-bit.zip" file in Finder. If that doesn't work, you can try moving the game files to another folder and running the app from there. Let me know if you're still having issues playing!