Default rotation direction for landscape apps
You can easily achieve this by automation. I prefer MacroDroid Being easy to learn and free

To understand how MacroDroid works and the settings required for your Android version, see  my answer

Your macro would look like this and you can tweak as you like

Trigger: Application Launched / Closed &rarr; Select your application

Action:  Force Screen Rotation &rarr;Force Landscape (or) Force Landscape 180 (Screen shot below shows possible options)

Constraints: None