Depends which iOS device you’re using, I think. On an iPad Pro from the past year or so, you can download a zip file of the code from github. There are also some pretty nifty usb-c hub devices that attach to the side of the iPad to connect USB thumb drives, SD and micro cards, etc. and you can transfer from the Files app onto them without a computer middleman.
I’m not sure how fringe this use case is at this point. The line between my iPad with a keyboard accessory and laptop is getting more and more blurry. Heck, I can code norns scripts using only my iPad.
That said I’m not really sure what went wrong here with the .zip extension. Seems like it should just work?
EDIT: Actually I just tested the process end to end and updated to 0.6.15 using only the iPad to download the file from github and transfer to SD. It worked fine. So maybe the issue is in the transfer to the Mac?