Update of my Plasma laptop went well, however, an update of my Plasma VM did not. I suspect that there is, or was, an upstream issue at Oracle, and if it's not already fixed, I hope for a resolution from them soon. There is a workaround, though, so all my VMs are usable for illustrating answers to forum questions. And that's really their only raison d'etre.
I'll explain. After I update each VM, I typically just shut it down instead of rebooting. That's because I usually have no reason to restart it at that time ... I just want to make sure it's up-to-date the next time I use it. It will load all the new packages if/when I start it again. If I do a shutdown now after an update has finished, the VM now enters an error state so serious that I need to use a long press on the power switch to recover. This doesn't happen just for Plasma, but for all of the VMs.
After restarting the host, and launching the VM to load all the new packages, if I execute another shutdown now command, it all works as expected. The end result of this adventure, for each VM, is that the update works, but it makes an update pretty painful. The workaround I mentioned: if I do execute a reboot after each update, then I can execute shutdown now without any problems. So, I'm convinced that the root cause of the problem is in the current VirtualBox, and as soon as the upgraded packages have been loaded, everything seems to work okay.
Since there is a workaround, and my four Solus VMs are quite usable now, I'm happy to wait for the next sync to see whether my idea is correct - that it's an issue that Oracle has already fixed.
