Revert navbar back to the right side of the screen under 270° rotation
As my investigation shows, Google calls it "Seascape Navigation Bar View" and deems it as a feature. This part of the code inside the Android framework determines whether the new left navbar layout should be used if 270° rotation happens. Making it still return NAV_BAR_RIGHT in the case effectively reverts the change. Tested side-by-side on a LineageOS compilation done personally.

Unfortunately for end users without access to source code, I don't know of a way to alter the behaviour yet: on older Android versions this change is supposed to be reflected in /system/framework/services.jar, but since Oreo it has both been split into a new /system/framework/services.jar.prof file and odexed, so currently available tools can't touch it as far as I know.