I’ve always uploaded the pck/binary together in a zip file and that seems to work. Maybe itch gets confused by the sandalone executable? I’ve used https://github.com/abarichello/godot-ci to automate exporting before, and here’s a really simple sr.ht example: https://git.sr.ht/~rcorre/jamcraft/tree/main/item/.build.yml#L13. Hope that helps!
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sr.ht is just a git repository host, similar to Gitlab/Github. I used that as an example because their build system is simpler than GitHub’s (which looked like this for our game this jam. Though as far as why yours didn’t work, it seems most games uploaded a zip file with the exe/pck, whereas your game was a single exe. The single exe probably should work, and the fact that it didn’t might be a bug with itch.