Unless there is something esoteric about my environment that I am not aware of, the version command looks broken on octo in Linux, I am using the RPM package octopuscli-7.4.1-1.x86_64 on CentOS 7:
$ octo version
.4.1
Looks like a bug to me, I was going to open an issue on https://github.com/OctopusDeploy, but got redirected here by advice in the template of the create issue screen.
Hi Eldomo,
Thank you for reaching out to us with your question about the CLI tool on Linux.
I’ve just tested this and it appears to work correctly for me on both CentOS and Ubuntu. It’s possible something may have gone wrong with your installation of the CLI.
Would you be able to try removing it and reinstalling? It may also be worth trying to upgrade to version 7.4.2 if that is a possibility for you.
Best Regards,
Charles
Hi Charles,
Thank you for testing that, you are absolutely right of course octo does indeed give me the correct value for version on a completely fresh installation of CentOS 7. There must be something off about my environment that I need to track down.
Kind regards,
Dom
Hi Dom,
Thank you for your reply.
If you happen to find out what the cause is please let me know - I’m curious! 
In the meantime, please get back in touch if you have any questions.
Best Regards,
Charles