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: Between the Extremes: Maybe we are just doomed to alternate between the extremes. (posted 2025-01-09 at 21:34:30). I do podcasts too!. You can listen to my latest podcast, here: OJB's Podcast 2024-12-04 Avoid Microsoft: If you don't really like computers much you could make things a bit better for yourself..