Firstly, the installation instructions you recommended have actually become quite stale. The latest version of DSC for Linux can be found here: https://github.com/Microsoft/PowerShell-DSC-for-Linux/releases. See also the Requirements/Installing DSC Packages content here: https://github.com/Microsoft/PowerShell-DSC-for-Linux/blob/master/readme.md
That being said, I believe the issue you described above to be a simple case of the wrong port. Port 5986 (not 5896) would be the default port for the CIM server.
Hope that helps,