On Leap 15.1 I have KDE configured to restore my last session on log-in. While
this successfully restarts applications like Firefox and KMail, one particular
application does not get started on Log-In, even when it was the in-focus
application during log-out: Quassel IRC (the client only version). Expected
behaviour for me would be that Quassel IRC is simply restarted on log-in, just
like any other application.

Sadly I don't have any good idea what logs would be relevant. Thus, let me know
if there's any log output I should provide.