Comment # 20 on bug 1013200 from Egbert Eich

(In reply to Max Staudt from comment #17)
> 
> This is clearly not the issue here. Patrick did the right thing: He
> uninstalled Plymouth *and* rebuilt rhe initrd. After this step, Plymouth can
> no longer hog the VT.

Ok, but the sddm greeter is calling abort() because it cannot connect to the
Xserver. This is either because the Xserver isn't ready for connections, yet or
sddm is using the wrong credentials - or something is grabbing it (unlikely).
When the Xserver is running but just showing a black screen one could try to
obtain the credentials from the Xserver command line and then try to log in:
>From a root shell (remote or after a VT switch) do:
 1. # ps aux | grep Xorg
    get the argument after '-auth'
 2. # export XAUTHORITY=<the_argument>
 3. # export DISPLAY=:0.0
 4. # xterm

Switching the DM would be something to try out as well...