The linux download file (at least for 64) is zip archive that internally contains another archive tar.gz
We are using butler to deploy Pixelorama directly from GitHub Actions to itch.io, and the file we are providing is the tar.gz archive. For some reason, it seems that butler/itch is also zipping that tar.gz file, while it shouldn't. Weirdly enough, this doesn't seem to be the case for macOS's .dmg files, so this seems like a butler bug regarding tar.gz files. Not sure if there's something we can do about it right now.
Sending individual files without zipping is possible. We are sending a dmg file for macOS and it is not being zipped. The issue seems to be occurring on tar.gz files for some reason. Tar.gz is generally preferred over zip in Linux, as they store Unix metadata such as permissions to execute, which Pixeloraman needs.