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: Just Get Over It!: In our divided society, people are likely to make extremely unpleasant comments about politicians. (posted 2025-04-09 at 20:00:45). I do podcasts too!. You can listen to my latest podcast, here: OJB's Podcast 2025-03-13 Embarrassing Nonsense: That might get the message across that we are sick of this embarrassing nonsense..