Not sure what happened but my laptop locked up with 42.3.
I had to hard restart it and now it autoboots up into something called ICE?
How do I get back to it starting KDE?
You can choose your desktop session (IceWM, twm, KDE/Plasma5, Gnome etc.) at your login screen.
Can’t remember how it was with Leap 42, but I think it should look similar to this screenshot I’ve just found. There, the option to change your desktop environment happens to be hidden in the popup menu in the bottom-left corner of the login screen. Depending on how your display manager looks (the program presenting the login screen: SDDM, GDM, XDM, SLiM or, in my case, KDM), that option might be hidden elsewhere (for example, under a button named »Other…«, »Session Type…«, »Desktop…« or some cog/gear icon).
Hope that helps. Cheers!
You are apparently seeing an auto-login to icewm.
When you are logged in that way, just logout. That should now give you a login screen. And make sure that you choose KDE (Plasma) for login on that login screen.
I’m guessing that the login screen comes from SDDM. In that case, the chooser is near the bottom left of the login screen. And be careful choosing. In my experience it is easy to accidentally finish up with the wrong choice.
Once you have made that change, it should remember your choice and your autologin will be to KDE in the future – until you do something to break it again.
Both you and unix111 of course are quite correct with your advice. Been using opensuse since 8.something so of course these screens are familiar.
But it isn’t happening that normal way. When the laptop boots it goes right to an IceWM login screen that is essentially blue with while strokes on it.
At the top of that screen are two “dialogs” on the left.
One dialog says Session and the options are IceWM and User / System Default.
The other dialog says Layout and only US is an option.
Choosing User / System Default doesn’t seem to really accomplish anything.
At the top in the same “bar” on the right are the two well familiar icons for Restart and Shutdown. Thats it.
And they do just that, no opportunity for me to get to a command line, though I’m not strong there with knowing what commands do what. I’ve got a book of linux commands but if you don’t know what tool to use… but I listen well. 
No option to just log out. Not even in the apps menu am I offered a log out option. Just restart/shutdown. Very odd I thought.
On the left center is the time/date and on the right a dialog with my login name and waiting for me to enter the password.
Nothing else on screen, no gear icons, no three little lines that somehow has become the icon for a menu in somebody’s mind, no other options.
Once the password is entered, I’m into what I suppose is the IceWM environment. I’ve never worked in it before. So I poked around there but not really sure where in YaST I might reset something or whatever I need to do to get back to KDE.
Doesn’t matter whether I login as Session User/System Default or not, always get to the same IceWM desktop environment.
I suspect this might take some command line magic. Some config file seems to have gone whack on me, but I’ve no idea which one or how to move forward. I can drive this dog out of a bog if someone can be my navigator…
What icewm packages are installed? Here I have a normal toolbar in IceWM, and these packages:
# rpm -qa | grep icewm
icewm-1.3.12-6.12.1.x86_64
icewm-config-upstream-1.3.12-6.12.1.noarch
icewm-default-1.3.12-6.12.1.x86_64
icewm-lite-1.3.12-6.12.1.x86_64
I can log out via a right click on the desktop.
What results if you Ctrl-Alt-BS twice?
What do you have for DEFAULT_WM= in /etc/default/windowmanager?
What to you have for DISPLAYMANAGER= in /etc/default/displaymanager?
If all else fails, then:
CTRL-ALT-BACKSPACE
Do that twice, and it should crash your icewm session and get you back to a login screen.
What icewm packages are installed?
All of the same plus one…
icewm-1.3.12-6.12.1.x86_64
icewm-config-upstream-1.3.12-6.12.1.noarch
icewm-default-1.3.12-6.12.1.x86_64
icewm-lite-1.3.12-6.12.1.x86_64
icewm-lang-1.3.12-6.12.1.noarc
I can log out via a right click on the desktop.
Yes I see the logout prompt as well. It returns me to the splashscreen awaiting a password / restart / shutdown.
What results if you Ctrl-Alt-BS twice?
If I do that from the login screen it just represents the login screen.
What do you have for DEFAULT_WM= in /etc/default/windowmanager?
What to you have for DISPLAYMANAGER= in /etc/default/displaymanager?
No such file under /etc/default.
Just these plain text docs
cdrecord
grub
grub_installdevice
nss
passwd
rmt
rscsi
star
su
useradd
And this backup file
grub.old
It does, back to the same iceWM splashscreen awaiting password, reset or shutdown.
It occurs to me that it’s acting like KDE isn’t installed anymore somehow. so I looked at YaST under iceWM and I see a lot of KDE installed and a lot not installed.
One that catches my eye… KDM KDE login and display manager vers. 4.11.22-5.29 is not installed.
But I don’t know if that’s a typically required component or not…
Can’t really seem to glean anything from YaST other than there are various “versions” for various KDE releated files installed.
Some are 5.32.0-1.3, some 5.8.7-1.1, some 5.32.0-1.19, 5.32.0-1.23, 4.14.33-1.4, 4.1-6.3…
I’m at a loss.
I was just using the laptop and it locked up so restarted and it’s not worked normally since.
Major typos there, should be:
What do you have for DEFAULT_WM= in /etc/sysconfig/windowmanager?
What to you have for DISPLAYMANAGER= in /etc/sysconfig/displaymanager?
What if you login on a vtty instead and run this:
WINDOWMANAGER=startkde startx
If it gives a permissions error, as root running:
chmod 4711 /usr/bin/Xorg
might clear the error.
No, that’s not an IceWM splash screen. It is the display manager login screen. There’s likely somewhere there that you can change what desktop you use.
If you installed KDE, then that is probably the SDDM login screen. Near the bottom left it probably says
“Icewm”, But there should be a selector to change to Plasma.
My brain keeps jumping out of gear today. 
That was supposed to be:
WINDOWMANAGER=startkde startx -- :1