PCTV Systems nanoStick T2 290e
It has experimental support since May 2011 in the media tree Git repository for v2.6.40. It is supported in kernel 3.0 and later.
The current Linux driver presents two frontends, one for DVB-C, the other for DVB-T/T2. T2 multiplexes are automatically detected and provided through the same API as DVB-T, giving maximum user-land compatibility. Support for T2 specific features are in development, but it's unclear whether broadcasters are making use of such features.
DVB-C does not seem to be fully supported with Linux, especially QAM256 (Windows officially only supports DVB-T and T2), according to mailinglist DVB-T2 LNA(?) damages DVB-C signal.
Be aware that some kernels broke the PCTV nanostick T2 290e. bugzilla.kernel.org