Unfortunately we don't have any experience on that, we forwarded your question to our community and hope, that a Dreambox User can share his informations about that.
This DM920 version does not have a DVB-C FBC tuner built in, the built-in dual tuner has 2 inputs (both have to be connected if you want to record something from a channel group than you want to watch at the same time).
Has an integrated dual tuner (1x tuner with 2 inputs) - another tuner can be upgraded separately. - You can therefore record two channels simultaneously ex works. Greetings