The issue appears to affect various users (including me!), but owing to the complexity of KDE/Plasma etc. it's not an easy fix. Some people get a blank screen, and nothing more, others just have the case of the GUI session taking forever to eventually load the desktop. Rather than having to manually load your X session each time, also try the following:
- Try setting the permissions of ~/.config to 775 or even 777, via "chmod g+rwx ~/.config -R" for the former, "a+rwx" for the latter.
- Also try resetting the ownership of all the ~/.config files to the correct local user, as some users reported issues with files owned by root after an upgrade. Use "chown user.user ~/.config -R"
Some users also found that removing all the KDE config files worked for them, so try:
mv ~/.kde ~/temp/.kde
mv ~/.cache ~/temp/.cache
mv ~/.local ~/temp/.local
mv ~/.config ~/temp/.config
And then reboot or restart the login manager, and try again. You can then manually copy back whatever app settings you need from .config or .local to get back your personal settings. It's a pain, but it has worked for some.
- Also try a dist-upgrade instead of a plain upgrade (as @"Mohamed Slama" reported in the original question!). Follow the howto for your distro... but basically it's recommended to get a terminal login and goto init 3 (kill graphical login) and then from a root screen session, issue the dist-upgrade command. Then see if it comes right.
- In my case, openSuse Leap 42.3 upgrade to 15.1, a dist-upgrade didn't work either. I had to move from the stable Leap 15.1 to Tumbleweed to get things going... but I did work on another machine, with the same issue, and traced the issue to the plasmashell. This has historically given me issues, and I often reset via a script that runs "kquitapp plasmashell && kstart plasmashell &".