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.
My latest blog post: Ask Doctor Google: Do I not trust doctors? Well, to some extent I do, but I would prefer an AI any day! (posted 2026-05-06).