Install a minimal xorg system
sudo aptitude -Ry install xserver-xorg-video-fbdev xserver-xorg-input-libinput rxvt-unicode xorg dbus dbus-x11
Install everything generic for nvidia blobs
sudo aptitude -Ry install dkms linux-headers-amd64 nvidia-installer-cleanup nvidia-support glx-alternative-nvidia libvdpau1 nvidia-modprobe nvidia-kernel-common
Patch your depot source to access nvidia-legacy-340xx-*_340.108-11_amd64.deb
echo "deb http://snapshot.debian.org/archive/debian/20211227/ sid main contrib non-free" >> /etc/apt/sources.list
Install nvidia-legacy-340xx-*_340.108-11_amd64.deb
sudo aptitude -y -o Acquire::Check-Valid-Until=false update
sudo aptitude -Ry install nvidia-legacy-340xx-driver nvidia-legacy-340xx-smi