I'm one of those who have been **** up with the last update 5.12:
- No login screen.
- No desktop.
- White screen always.
- No toolbar nor plank.
- Unable to recover from lock screen .
- Only commands works (fortunately I've a keyboard shortcut to kconsole).

After many hour trying posted "solutions" with no luck (even reinstalling the full installed packets with synaptics), I've realized that login with root user in an alternative session, desktop was shown and many things seemed to work. I've tried with my user's home folder .config, .gconf, .kde and many others things, but finally renaming .cache folder solved my problems. One new .cache folder is created automatically and now everything is working fine, but i need to configure again a lot of preferences I've lost with this update. I cant believe this piece of **** has been released but I hope this post could be helpful for somebody.

Although my upgrade went flawlessly, the obvious lesson here is to backup your system before upgrading. I use fsarchiver to periodically take a snapshot of my system. Particularly with a system thats on the cutting edge like Neon. I also use Bleachbit to clear out my cache & other junk before updating. Another thing to do if you don't want breakages is to stick to a distro like Debian or Solydk.
Unfortunately having the latest packages & Stability don't often go hand in hand in the Linux world.

hastaelnabo2000 wrote:I'm one of those who have been **** up with the last update 5.12:
- No login screen.

Did you upgrade also to mesa 18 at the same time?

It could be this bug: https://bugreports.qt.io/browse/QTBUG-66348

If stability is your priority, you might want to consider openSUSE instead since they have a large automated integration test suite (http://open.qa).

I've never been able to figure out exactly all the automated tests that Ubuntu runs.

Upgrade was done on a regular basis, with Discover updates notifications. Other times I have had some other unimportant failures: applications that stop working, others that need to be updated, ... something normal. This time the problem is that I was literally without system, the login screen was all white and the desktop all black, without any functionality and, once recovered, I lost almost all my personalizations (a couple or three days re-configuring and solved).
I have tried several distributions and now I work with this one because I like its fluidity and performance and I do not intend to change it, but the last update I think has not been done well given the number of posts with problems related to this update.