Ok, I guess first of all is the question: Why do you need to have remote access to the vCSA directly? What are your scripts doing that require access to the underlying operating system?
vCSA is a Linux-based appliance, and you cannot install other software or agents inside. This most certainly includes PowerShell Core.
If you can say what these scripts do, it's possible to find an alternate method, because there shouldn't be any valid reason for needing regular, remote access to the vCSA's OS to interact with vCenter.