I guess if no one has any more suggestions a re-install will be in order. Does anyone have any suggestions for diagnostics before I do that, I guess since I seem to be the only one having this issue in TW it must have been a glitch somewhere!
Just to check it out I downloaded the latest ISO and installed it OK in a VM which proved to be fine as I expected.
I have today installed a new HDD and actually installed openSUSE TW on it, the desktop options all work on that. Although I still have the old HDD in the PC so that I can move my data over and it will then be removed. Sadly it’s just out of warranty by about 1 month!
Yeah, it probably would have made the desktop completely unresponsive, or not even starting (the latter happened when I removed kactivitymanagerd a few days ago, the desktop only came up when I moved it back).
Although, it might be triggerZ’s problem on Fedora with 5.9.5 (the older version might behave differently)… Or not.
I still think that this must be related to kactivitymanagerd somehow.
So try to remove its database, i.e. delete (or rename) the folder ~/.local/share/kactivitymanagerd/ and see if it helps.
You might lose your application menu favorites though, and the list of recently used applications/files.
All running Tumbleweed. The 2 that are defective have the configure desktop issue along with the inability to add a panel. removing kactivitymanagerd makes no difference.
There is a crucial difference: The desktop and my wife’s laptop hadn’t had any updates applied prior to this one for at least 2 weeks. My laptop (the working one) gets zypper dup’ed every couple of days. I just say that incase there was a plasma5 patch that ran a migration script which was missing if you jumped that update (long shot). BTW my desktop is NVIDA and openGL works fine and my wife’s laptop is Intel which has openGL working also.
In short, it is (can be) caused by kpluginindex.json files (which contain a cache of installed add-ons) that cannot be read.
Additionally, kpackage 5.43 changed the file format (the files are compressed now) and cannot read older files anymore (which is a bug of course, but not specifically related to Plasma 5.12, which explains that triggerZ has it with 5.11.5).
So delete all kpluginindex.json files in all subfolders of ~/.local/share/plasma/ and everything should work again.
If it also affects a fresh user account, such files may be in /usr/share/plasma/, so check that too.
Apparently they get written system-wide if you run Plasma as root… (ever heard that you shouldn’t run a desktop/graphical session as root? )
In particular, it seems /usr/share/plasma/plasmoids/kpluginindex.json is causing this, so delete it if it exists.