Last time I had test-wise changed to Xorg driver just to see if the good colours come from the NVidia driver. (I used to use Xorg with 18.04 as the NVidia driver caused some issues 2 years ago). This morning, when I started the system, I can't change the driver. Everything looks like Windows in Safe mode.
see from " Manually adding your drivers via the terminal:" from the link below:
Okay, I installed the wrong driver and now I can't boot/my graphics are shot!:
Thanks, Wolfman, I will reinstall the system once more. It happenes on my desktop which is my guinea pig to make sure that the change on the laptop works without mistakes. It was already a lesson from 18.04 not to play around with the graphic card driver. Being in my second LTS round, I finally learned "never touch that part".