Why does my ubuntu 18.04 get stuck on the 'purple' screen after logging in?

Question

Please provide me with a detailed answer explaining why my Ubuntu 18.04 gets stuck on the purple screen after trying to log in. Is it some bug in Ubuntu or do i need to install some additional drivers or something? I have an AMD RADEON GRAPHICS Chip in my laptop (in addition to intel i5) which isn't configured yet and which might be causing this issue. Are there any commands I can use on that purple screen to get around it because right now i can only avoid it by performing a force shut down of the system using the power button.

Solution

There are two relevant bug reports on the "purple screen" in Ubuntu 18.04 LTS. Many people have encountered difficulties including myself. However my problem seems different than the two bug reports so there might be more in the future regarding this issue.

Here are the two bug reports:

• [regression] Password accepted but login fails (blank purple screen and mouse pointer only)
• [regression] Ubuntu 18.04 login screen rejects a valid password on first attempt. Usually works on the second attempt

My problem/solution not in the bug reports was this:

• Upgrade Ubuntu 16.04 LTS to 18.04 LTS = 5 desktop environments

Comments

[WinEunuuchs2Unix]

The Intel i5 iGPU (integrated GPU) is supported automatically. It is the Radeon and nVidia GPUs that usually require extraordinary driver support.