NVIDIA have released the latest Vulkan beta driver 440.66.02, and details are here:  https://developer.nvidia.com/vulkan-driver

The kernel-related code seems to be unchanged from 440.64, and the Kernel 5.6 patch for that version still applies, and can be found here: https://gitlab.com/snippets/1945940

The driver then compiles OK:
.................
ld -r -o /home/rgadsdon/kernel/NVIDIA-Linux-x86_64-440.66.02-custom/kernel/nvidia-modeset/nv-modeset-interface.o /home/rgadsdon/kernel/NVIDIA-Linux-x86_64-440.66.02-custom/kernel/nvidia-modeset/nvidia-modeset-linux.o /home/rgadsdon/kernel/NVIDIA-Linux-x86_64-440.66.02-custom/kernel/nvidia-modeset/nv-kthread-q.o
MODPOST 4 modules
CC [M] /home/rgadsdon/kernel/NVIDIA-Linux-x86_64-440.66.02-custom/kernel/nvidia-drm.mod.o
LD [M] /home/rgadsdon/kernel/NVIDIA-Linux-x86_64-440.66.02-custom/kernel/nvidia-drm.ko
CC [M] /home/rgadsdon/kernel/NVIDIA-Linux-x86_64-440.66.02-custom/kernel/nvidia-modeset.mod.o
LD [M] /home/rgadsdon/kernel/NVIDIA-Linux-x86_64-440.66.02-custom/kernel/nvidia-modeset.ko
CC [M] /home/rgadsdon/kernel/NVIDIA-Linux-x86_64-440.66.02-custom/kernel/nvidia-uvm.mod.o
LD [M] /home/rgadsdon/kernel/NVIDIA-Linux-x86_64-440.66.02-custom/kernel/nvidia-uvm.ko
CC [M] /home/rgadsdon/kernel/NVIDIA-Linux-x86_64-440.66.02-custom/kernel/nvidia.mod.o
LD [M] /home/rgadsdon/kernel/NVIDIA-Linux-x86_64-440.66.02-custom/kernel/nvidia.ko
make[1]: Leaving directory '/usr/src/linux-5.6-rc6'

Robert Gadsdon.  March 18th 2020.