Cuda 10.2.89-440.33.01 Ubuntu 18.04

Hello, I just Downloaded the last Cuda Toolkit following:

I succesfull installed it but I am unable to get nvidia driver loaded on startup. I am running Ubuntu 18.04 on an Acer 8915G Laptop using a GT 555M Nvidia chipset with 2GB dedicated ram. In the boot log I can see:

[ 4.593109] nvidia: module verification failed: signature and/or required key missing - tainting kernel
[ 4.604634] nvidia-nvlink: Nvlink Core is being initialized, major device number 238
[ 4.605329] NVRM: The NVIDIA GeForce GT 555M GPU installed in this system is
NVRM: supported through the NVIDIA 390.xx Legacy drivers. Please
NVRM: visit for more
NVRM: information. The 440.33.01 NVIDIA driver will ignore
NVRM: this GPU. Continuing probe…
[ 4.605333] NVRM: No NVIDIA graphics adapter found!
[ 4.605480] nvidia-nvlink: Unregistered the Nvlink Core, major device number 238

I am just new with cuda and I am unable to understand if I should load driver 390.xx or if the current toolkit should be able to load the 440 driver with this hardware. If I run:

nvidia-smi -a I get:
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 can I get the driver to be loaded ? Which version of the driver should I load?
Thank you very much for any help.
Marco Bisio