Problem solved-Ubuntu 18.04 cannot enter the graphical interface after installing the Nvidia graphics driver
First, check whether the version of your Ubuntu 18.04 image is ubuntu 18.04.4. If it is, it is recommended to download the higher version image again.
For example, in ubuntu18.04.5, gdm3 and nvidia driver conflicts caused by the Ubuntu18.04.4 kernel bug, making gdm3 unable to start the graphical interface normally, and gdm keeps trying to start the result is the screen flicker.
The above phenomenon will not occur after replacing the higher version image.