Estimate Time Is Super Slow

[philsmd]

you probably also need to install the ICD separately, e.g.
sudo apt install nvidia-opencl-icd-390

or ocl-icd-dev, ocl-icd-opencl-dev (i'm not totally sure which you need, but the nvidia one seems to be the one that makes most sense)

if you instead install the driver from https://www.nvidia.com directly, the ICD will be installed together with the driver directly/automatically without any need to change something. but I guess the ubuntu package maintainers splitted them into 2+ packages