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: Respect the Flag?: Find me a Maori flag and I will burn it. (posted 2025-05-31 at 18:45:40). I do podcasts too!. You can listen to my latest podcast, here: OJB's Podcast 2025-04-24 Go Winston!: If a politician want's to empower the majority view then I'm all for it..