CUDA isn’t 32-bit only… there’s a 64-bit libcuda.so.1 shipped with the driver and a 64-bit CUDA toolkit is available at CUDA Toolkit 11.7 Update 1 Downloads | NVIDIA Developer
As for the fbdev thing, Gusar is correct; the nvidia-drm driver does not implement an fbdev console. But you should be able to use vesafb or efifb, depending on your system setup. vesafb isn’t technically supported at the moment, but we’re making an effort to make it work better overall.
The main reason, currently, that we don’t implement a framebuffer console is that when a kernel module is plugged in as the framebuffer console driver, it can’t be unloaded. We need to be able to support unloading the kernel module.