This intrigued me. I was once told by a respected windows sysadmin that you couldn’t upgrade from 2016 to 2019.
But it’s documented that you can: https://docs.microsoft.com/en-us/windows-server/upgrade/upgrade-2016-to-2019
I’ve always used the opportunity to start with a fresh VM and a nice clean install of windows and then upgrade Esri as a part of that (from one machine to another):
https://enterprise.arcgis.com/en/portal/latest/administer/windows/migration-strategies.htm#ESRI_SECT...
so I’ve never done an over the top of windows server, but I have recently upgraded my windows 10 based dev environment to win 11 and it was seamless.
ultimately if you clone/snapshot each machine, then you have a rollback. I like your approach of config server, webs server etc.
exciting times. I’d be interested to hear how you get on?
Scott Tansley
https://www.linkedin.com/in/scotttansley/