I've used Ubuntu 16.04 on my laptop for more than 1.5 years without major problems, but yesterday it hang during start-up. I spent some time trying to fix it and eventually decided that it would be easier to reinstall, so I downloaded Ubuntu 18.04 and installed that. However Ubuntu 18 is showing strange artifacts on the screen; blinking blocks of light blue dots all over the screen, and sometimes diagonal gray stripes or blocks and/or little cluster of black dots (see for example the screenshot below). It does this on both my laptop screen as well as on my secondary monitor.
This is what I tried so far to fix it
I did't check what drivers where installed initially, but one of the first things I did was make sure that nvidia drivers were installed using
sudo ubuntu-drivers autoinstall
ubuntu-drivers devices is
== /sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0 ==
modalias : pci:v000010DEd00001618sv00001558sd00007503bc03sc00i00
vendor : NVIDIA Corporation
model : GM204M [GeForce GTX 970M]
driver : nvidia-driver-390 - distro non-free recommended
driver : xserver-xorg-video-nouveau - distro free builtin
I then tried switching to the X.Org Nouveau driver (via Software & Updates -> Additional Drivers -> Using X.Org X -server). However this caused my laptop screen to revert to a 640x480 resolution and no option to change that (
xrandr -q only showed 640x480)
Next I tried adding the graphics-drivers PPA repository and installed nvidia-driver-396. This didn't solve it and even introduced new problems, such as a completely black top menu and background at startup, only to become visible when you click on the 'applications' button in the side bar. I also tried nvidia-driver-410 but that resulted in a completely black screen which I could only fix by booting into recovery mode, purging the 410 driver and reinstalling the 390 driver.
So what else can I try to fix these graphics problem? Or is my only option to reinstall Ubuntu 16.04 again?