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: Garbage: Democracy dies in darkness, especially when it is buried in garbage! (posted 2024-11-01 at 12:31:14). I do podcasts too!. You can listen to my latest podcast, here: OJB's Podcast 2024-08-22 Stirring Up Trouble: Let's just get every view out there and fairly debate them..