I am using KDE neon 5.21 with Ubuntu 20.04 LTS on a HP Elitebook. The system is running pretty smooth but there is one major inconvenience:

The desktop sometimes becomes extremely laggy. The mouse is still moving smoothly but every other action (moving windows, typing text, every click) takes a delay of about one second. This happens after one of the following actions (still discovering more):

* specifically when closing the application `guvcview`
* applying different window decoration style via settings
* applying different compositor settings
* adding a property to a window to force it to take a specific size

Quitting and restarting the session usually fixes the issue, but not always. I have also tested other distributions such as openSuse KDE on this machine and the issue is exactly the same.

The only thing that fixes this issue permanently is swtching the compositor from OpenGL 2.0 or 3.1 to XRender. So I think OpenGL might be the culprit somehow. I still would like to use OpenGL as it feels more smooth.

Here is the output of `inxi -G`, in case that might be helpful.

```
Graphics:  Device-1: Intel UHD Graphics driver: i915 v: kernel 
           Display: x11 server: X.Org 1.20.9 driver: modesetting unloaded: fbdev,vesa 
           resolution: 1920x1080~60Hz, 2560x1440~60Hz 
           OpenGL: renderer: Mesa Intel UHD Graphics (CML GT2) v: 4.6 Mesa 20.2.6

```

I can, of course, provide more output if desired.