My box is running now for a whole night&day without problems, including multiple hours of active working with libreoffice writer.
Obviously this solution works: -------------------- create folder and file /etc/X11/xorg.conf.d/20-nouveau.conf and put in: Section "Device" Identifier "NvidiaCard" Driver "nouveau" BusID "PCI:01:00:0" # PCI bus address of the Nvidia GPU here EndSection -------------------- I'd recommend debian install / upgrade procedure to care for a similiar solution, maybe adopted to the proper debianic way.