Just want to add a note in case it happens to anyone else.
After updating to plasma 6 at first the desktop wouldn’t load and I had to run the command to install plasma-desktop-data from Plasma 6 update, desktop won’t load - Help - KDE Discuss.
After doing that the desktop background would show up but there was no dock/taskbar anywhere on the screen. Before the update the taskbar on the left side of the screen. Edit: I also had a weather widget which now says “unsupported” when I try to re-add it so maybe that’s why?
I tried to “reset” it from the system settings by re-applying the global theme (“breeze dark”) but that didn’t do anything.
After playing around more I had to right click on the desktop wallpaper, choose “enter edit mode”, click “Add panel” and then “Default panel” to get it back.
I’m sorry this happened. If you’re using Neon, it’s a known issue that’s being worked on; see Plasma panel is broken on plasma 6 - #3 by ngraham.
I had similar/same issue, which I reported on bugs.kde.org. However, not only my panel was gone, but all controls/menus you’d get with the right mouse button, so couldn’t restore normal desktop/GUI. All there was was a large ‘desktop’ rectangle and small one, and a plus that adds more, and a search. I don’t know if it had anything to do with the 16:10 2K monitor. We had to switch that PC from KDE Neon GNU/Linux to GNU/Linux Mint XFCE, so unsure I can ever find out what happened. If KDE programmers/developers are sure they want to find out, I guess I can try once more, but someone in Libera Internet Relay Chat (IRC) said Neon is ‘almost-rolling release’ I shouldn’t put on family PCs for average users rather than Kubuntu LTS GNU/Linux…