Same problem here, with the Kubuntu 20.06. I’ve installed it yesterday, and first I had problems with the kscreen2, that I finally had to disable, and after a massive update, I’ve started to have problems with the panels. It basically disappear everything from the desktop, and then after stopping and starting back Plasmashell a couple of times, panels are back. It has happened twice.
If someone could tell me what kind of information is needed to see what may be happening, I’ll be happy to provide it.
Regards

As mentioned before: please follow this on the bug report.

Hi Mamarok,
If it helps, I realized that in my case, strictly, it is not bug. It is the screenpad of the Asus laptop, which is a touchpad with a touch screen (like a smart phone), so the main screen is acting like a secondary screen while the screenpad is considered as the main screen.
It if fixed by switching the [ScreenConnectors] in plasmashellrc file, that is in in the ~/.config folder, then restarting the plasma (kquitapp5 plasmashell && kstart5 plasmashell &)
Thanks

Mamarok wrote:As mentioned before: please follow this on the bug report.

Right, that is a totally different issue, I split your posts of in a new topic. I still suggest filing this as an informative bug, as screenpads are getting more common, so maybe a different configuration is needed in the future.