The update from 418 to 430 can be done smoothly with an option that is somewhat hidden. Open the main menu with the Super
key, and search for "software and updates". The app should have several tabs, including "additional drivers". Go to that page, and you should see the following.

Select the newest driver (in this case 430), apply, and restart.
UPDATE
I just realized if you do it this way, e.g. install CUDA 10.2 first, which comes with the older 418 driver, then install a newer 430 video driver, the next autoremove will remove both CUDA and the older driver. If you try installing CUDA again using the .deb file, it will attempt to replace the 430 with 418 drivers! That is bad.
According to this thread on the nvidia forum, we can avoid the CUDA installer downgrading our display driver by using the local .run
file, with the --toolkit
option, and not the deb
file installer. Also, after installing this way, there will be some missing libraries, which are described in section 7.3.1 here. In short:
sudo apt-get install g++ freeglut3-dev build-essential libx11-dev \
libxmu-dev libxi-dev libglu1-mesa libglu1-mesa-dev