Hi,

I first tried to upgrade a KDE neon bionic based virtual machine to latest KDE neon after getting the upgrade pop up:

- After reboot, the login page shows up fine, and the login completes successfully
- an error message from virtualbox guest additions shows in a pop up notification for a second before the screen going all black
- Powering off the machine from the virtualbox menu shows a dimmed desktop exactly like when the machine is paused, allowing me to read the pop up; it says:

> error: VBox Client: Failed to get display change request, rc = VERR_NOT_IMPLEMENTED...

Then, I tried a fresh installation from the latest iso downloaded from KDE neon website:

- Everything works fine without Virtualbox additions
- Installing virtualbox-guest-dkms and virtualbox-guest-utils work fine, and the system can reboot as expected
- virtualbox-guest-x11 seems to cause the problem described above; as soon as I install it on a clean VM, I get the same error message, the same black screen right after the pop up notification described above.

The problem seems to be easy to reproduce, so, I am surprised not to have found anyone complaining about this issue.

I have however found many reports of problems related to 3d acceleration, and the new 'SMSVGA' display option on the host virtualbox application machine settings.
So, I have to specify my host machine is a Kubuntu 18.04 installation, and my Virtualbox application does not have this option yet, 3d acceleration is not enabled on my guest.

Maybe I am missing something obvious, any help to fix this issue will be appreciated. Thank you for your time.

What is the host OS, and what version of Virtualbox? Is Virtualbox the latest version?

The host is Kubuntu 18.04, virtualbox is 5.2 installed through bionic repositories.

lyndhurst wrote:The host is Kubuntu 18.04, virtualbox is 5.2 installed through bionic repositories.

You will want to upgrade Virtualbox to a version that supports the new 20.04 systems.

Method 3 from here is probably the best way to go:
https://itsfoss.com/install-virtualbox-ubuntu/

I'd suggest uninstalling all existing virtualbox packages first.

Thanks for your help, this is the only thing I have not tried yet, was not sure it was related.
Anyway, I will try first thing tomorrow morning, and update this topic with the outcome.
Thank you for the link as well.

I have not tested extensively, but everything seems to be working fine now.

I will add for anyone reading this thread while facing the same problem that I downloaded the Virtualbox extension pack matching the new Virtualbox version installed on my system from the website as well.

Thank you again for your help.