Arc uses a method of uploading the game to itch.io that allows people to use the launcher on Computers to update the game easier.
Problem is that it sometimes decides to put the APK inside a zip file. If your file manager can extract zip files, you can install it from there.
Otherwise, go to the Patreon or Subscribestar page for the game and use the public download links, they’re the same version than the one posted here on itch.io