Hello - in trying to upgrade Windows 2016 distributed deployment form 11.1 to 11.2, the portal upgrade, post upgrade and web adaptor installs went fine and I was able to see the portal at 11.2 through its web adaptor.
BUT - after uninstalling the host site web adaptor I then ran the Setup.exe for ArcGISServer. Took about 2 hours, the post upgrade launched in my Chrome browser, but no local host. FQDN name for manager did not work either.
I then looked for the ArcGIS Server windows service and it is not there. I am doing a full uninstall of ArcGIS Server on the machine and will try a re-install, but I have no confidence that it will work.
@JonEmch