Nvidia may not be working in Ubuntu 19.04 environment

Nvidia-driver-435 should be installed in my Ubuntu 19.04 laptop through Software&Updates. However, it may not be functioning since the graphic card might not be detected. See the following command :
$ nvidia-smi
NVIDIA-SMI has failed because it couldn’t communicate with the NVIDIA driver. Make sure that the latest NVIDIA driver is installed and running.

$ nvidia-detector

nvidia-bug-report.log.gz (94.5 KB)

Please disable secure boot in bios.

I am assuring this might be the solution to the problem. However, my laptop won’t be able to boot Ubuntu after I disable secure boot. I am finding a way to tackle this problem. Thanks by the way

The easiest way to have Ubuntu+nvidia driver+secure boot enabled is to reinstall Ubuntu and during the installation, choose to “install third-party software”->nvidia driver. This will enable and guide you through the module signing setup, needed for secure boot.