The tool that's used to submit a binary to Apple only runs on macOS. Short of something like a hackintosh (which is against the macOS license) or maybe Darling, it's not clear how one would do the submission without a mac.
This is a real issue for me, as my open source project is a cross-platform game development tool. It used to be that it was possible for someone to click a button and get Linux, Windows, and Mac distributions - but now the Mac side is proving more and more difficult.
