I recently booked an itinerary, containing a leg on Qatar's A350. I found an image on seatguru showing power outlets. Did somebody fly the A350 in eco and can tell me if I can use a standard German laptop charger (230V, 50Hz) or do I need an adapter?
Based on the logo on the socket, this is an "EmPower" socket - which isn't surprising as they are the most common type of these sockets on airplanes.
You can find a datasheet for these types of sockets here, that claims they are "Compatible with plugs from over 170 countries", and then specifically shows compatibility with multiple forms of 2-plug European power sockets (earthed and unearthed)
So yes, this socket will accept your German power plug, along with plug from most other countries, without an adapter.