I'm having similar issues. Framerate of about 1 frame per second. I find that the game is using less than 10% cpu and less than 200MB ram. Windows 10. Geforce GTX 1060 or thereabouts. The lag begins only after the unity logo (in the game). No command line output.
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Tried the latest version (demo, linux), no, I can still only go in 8 directions. I should add that I didn't notice this was going on for a while when I started playing, it still has variable speed, I think, so it feels more fluid than it possibly is.
Another issue, file-roller (which is standard) has trouble unpacking the .gz. It would show a tar file inside, named the same as whatever the .gz was called, and it wouldn't be able to open that tar. Changing the extension to .tar.gz fixes the problem.