If there is no rotate option available for displays connected through a dock, check that DisplayLink software is installed.
If the DisplayLink Manager is installed do the rotation through that instead of using the System Preferences: Displays rotate option (which is not available). If this fails, check the DisplayLink software is fully up to date.
I usually write a blog post about once a week. The latest post can be viewed here: Too Many Road Cones: I think it is clear, there are too many road cones! (posted 2025-07-18 at 16:55:03). I do podcasts too!. You can listen to my latest podcast, here: OJB's Podcast 2025-06-28 An Empathy Deficit: They end up reducing the total empathy in the world..