KWin crashes on startup on KDE Neon developer edition

[David Hurka]

> > Cannot mix incompatible Qt library (5.15.3) with this library (5.15.4)
> > [...]
> 
> The first line looks most interesting to me.
> I have libqt5core5a 5.15.2+p20.04+tunstable+git20200516.1232-0 installed.
> It is the only version known to aptitude.
> I think this is what counts as Qt 5.15.3, because of the KDE patch
> collection story.
>
> [...] 
>
> I can not investigate further right now.
> If the issue automagically fixes with a future update, I will tell you.

Hooray, the issue fixed automagically now! :)

Aptitude has installed libqt5core5a 5.15.4+p20.04 now.

My previous desktop configuration was lost, however. :(