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: End of Another Error: I have go to say that this is both a happy and sad milestone in my life. (posted 2025-12-19 at 22:16:32). I do podcasts too!. You can listen to my latest podcast, here: OJB's Podcast 2025-11-06 Democracy v Bureaucracy: It's not left versus right which I am complaining about: it is bureaucracy versus democracy!.