Being a Russian citizen, I am interested in obtaining a tourist visa to Luxembourg. Usually when you apply for a Schengen tourist visa, you require a proof of accommodation and usually a booking.com reservation is alright (in case you stay at a friend's place or something). But Luxembourg doesn't accept booking.com reservations and they ask to provide a certificate of prepaid accommodation.
What can I do in case I don't want to stay in a hotel and thus cannot pay for it? Is it possible to make a German Schengen visa with plane tickets arriving in Luxembourg and departing from Cologne?