NVIDIA Driver 384 Can't be installed correctly on Ubuntu 16.04

I used the following commands to install

sudo add-apt-repository ppa:graphics-drivers
sudo apt-get update
sudo apt-get install nvidia-384

Installation appears fine with no errors, but I don’t see any NVIDIA folder under /dev.
When I run smi,

modprobe: ERROR: could not insert ‘nvidia_384’: No such device
NVIDIA-SMI has failed because it couldn’t communicate with the NVIDIA driver. Make sure that the latest NVIDIA driver is installed and running.

How do I correctly install the latest NVIDIA driver correctly?

are you referring to the driver NVIDIA-Linux-x86_64-384.90.run?

I have the same problem.

I am trying to install the driver for a NVIDIA Quadro M4000 8GB on Ubuntu 16.04.

have you tried installing the driver in a complete non-gui mode?

I found this video to be very helpful.
Install Nvidia Driver on Ubuntu 16.04 (GUI Method for Beginners)

What is the return of lspci? Does it list Nvidia GPU hardware?
You may use different driver installation methods that include installation from .deb or .run.
I am just wondering if you have managed to resolve the issue.