Private clouds are not currently supported. Someone else also asked about this https://twitter.com/SkakmatP/status/1337486621688655874
Believe your current golang plug-in would still be used. Though, would need to build a terraspace plugin in Ruby and maybe even make some terraspace core changes to make it work. Would like to add support. It’s a matter of time. Also, will consider PRs. No sweat either way of course. 
Just wanted to note it for others.