First off, thanks so much for the clear, concise, truly excellent answer. I did have one question:
"If the second vcenter also has its own SSO installed on the same machine and the second SSO was installed in multisite mode (expected to be yes, since the primary goal is linked mode), you need a clean up of vmdrd of first SSO.
VMware support has specific utility to get that done, Please file a case to get support."
I'm working in my home lab at the moment and do not have VMware support. Is there a way to accomplish this without filing a support ticket?
Secondly, does the SSO database installation leave anything behind in Active Directory? I recall having another issue with a failed install in which the workaround was having to rename the second vCenter host in order to reinstall. I believe this was an AD issue. Sorry to be so vague, if this doesn't sound familiar I can dig up the actual KB.