Comment # 1 on bug 1175991 from Neil Rickert

I don't notice this, because the scripts that I use already set SSH_ASKPASS

But I did notice what seems to be a related bug, and might be the cause of your
problem.

Previously, so ssh programs were in "/usr/lib/ssh".  But now they have been
moved to "/usr/libexec/ssh".  But there's one exception.  It seems that
"ksshaskpass" is still in the old place (in "/usr/lib/ssh") and has not been
moved to "/usr/libexec/ssh".

Maybe try putting a symlink in "/usr/libexec/ssh" for ksshaskpass, and see if
that solves the problem.  I think the KDE maintainers need to fix this, but the
symlink might be a possible temporary workaround.