This morning I installed the latest updates for KDE Neon which included Plasma 4.9.5
After the update the desktop is not working anymore. Every startup there is a message with ksmserver error. Most desktop components are not working.
Has anyone the same problem and maybe fixed it somehow?

Not sure, if it's related, but here after update I get black screen after startup, though I'm on VirtualBox.

I can see the same problem both in Vbox and on a physical host.
In ~/.xsession-errors:

9:21% grep 'failed to launch' ~/.xsession-errors
ksmserver: autostart service "/etc/xdg/autostart/kdeconnectd.desktop" failed to launch
ksmserver: autostart service "/etc/xdg/autostart/kwrited-autostart.desktop" failed to launch
ksmserver: autostart service "/etc/xdg/autostart/kdeconnectd.desktop" failed to launch
ksmserver: autostart service "/etc/xdg/autostart/kwrited-autostart.desktop" failed to launch
ksmserver: autostart service "/etc/xdg/autostart/kdeconnectd.desktop" failed to launch
ksmserver: autostart service "/etc/xdg/autostart/kwrited-autostart.desktop" failed to launch
ksmserver: autostart service "/etc/xdg/autostart/kwrited-autostart.desktop" failed to launch
ksmserver: autostart service "/etc/xdg/autostart/kdeconnectd.desktop" failed to launch
!ksmserver: autostart service "/etc/xdg/autostart/mpd.desktop" failed to launch


The desktop is partially usable after that but it tales a long time until I can do anything.

I have submitted BZ

https://bugs.kde.org/show_bug.cgi?id=379254

if you have any additional info, please add it to that BZ.

Alex

The upstream developers decided to revert one of recent changes. Until Neon provides new packages, you can fix your system to workaround this.

The problem appears when ksmserver cannot start some process listed in /etc/xdg/autostart
This can be due to two reasons:
(1) old .desktop files in that directory that are not needed anymore
(2) .desktop files that contain incomplete path that now is not resolved properly

An example of problem (1) is a new 'kwrited' package - it does not contain neither 'kwrited' executable not its desktop file - but for some reason, upgrade did not purge
/etc/xdg/autostart/kwrited-autostart.desktop

An example of problem (2) is 'kdeconnectd' package - its .desktop file has a line

Exec=lib/x86_64-linux-gnu/libexec/kdeconnectd

5.9.4 version was able to find the file which is at /usr/lib/x86_64-linux-gnu/libexec/kdeconnectd, the new version cannot

Workaround
==========

1. Remove obsolete files in /etc/xdg/autostart. You can do this manually or do something like that

# apt remove --purge kwrited
# apt install neon-desktop

2. Edit files in /etc/xdg/autostart that create problems and have incomplete path spefification, e.g. for kdeconnectd change the exec line to

Exec=/usr/lib/x86_64-linux-gnu/libexec/kdeconnectd

***
After that login works fine, without any delays and error popups.

Alex

I think there was an update today. I get black screen @ startup so most probably something is still broken. I've looked into .xsession-errors but I can't grep any "failed" so I'll try to get this file from VM manually and post it here.

Thanks for this info. I deleted some faulty autostart entries. Hope the message doesn't come anymore. It's only sporadic.