Hi Mark,
Just found a few additional docks - the
Diamond Multimedia Ultra Dock also supports Ubuntu and looks like it would fit your requirements. Also,
this Lenovo Dock says that it is OS independent, but that's less specific, so I'm not certain on that one, but I suspect it would support Ubuntu. This
Targus Docking Station states that it explicitly supports Ubuntu. So now you have a few options
Regards,
Andrew