That is not how you do it for KlipperScreen at least:
You must add the rotate screen to KlipperScreen config file.
You will hardly ever use the operating system itself anyway so don’t bother. Follow the above to rotate the display on KlipperScreen level and call it a day
I am having the same issue as Chris, so I tried to follow through with your recommendation but there doesn’t seem to be any setting in the directions/descriptions that point to rotating the screen. Do you mean to say you take the comments you would normal save in the 90-monitor.conf file and save them inside the KlipperScreen.conf file?