Apparently this is still a problem! I have a iMac running Catalina and I purchased and downloaded the latest file for Mac. (Ive also tried the older file) I do not get a zipped file.. it seems to be a regular file (160mb) and it just gives the same dreaded error.. I do not even have the option to "unzip" because it is not compressed or "zipped". I do not have a PC at my disposal to try and covert the file and the terminal commands are not working.. this is frustrating.. Help Please... again archive utility isn't even an option for me..
The file you download here on Itch is indeed a zip file (although it may not obviously show up as one on your computer depending on how it is set up). I would recommend download a unzip software such as the one mentioned in the post above (Keka) and try using that.
(You need to get the file unzipped before you can try any of the other tips such as terminal commands etc.)