Despite checking the "Hide window on startup" option in Configure->Behavior->General behavior, Konversation window is displayed whenever I log in.
Is Konversation auto-started via session restore, or do you have it enabled in autostart folder?
It is enabled in autostart.
I suspect that next to Konversation having been added to autostart, it was also covered by session management. And as both are sadly not integrated, this resulted in Konversation being started 2x, once by session restore as well as autostart later on. And any second start is always interpreted as activation, which is handled by ensuring the window is shown. Next to that, session management support in Konversation had a bug in not remembering the window state properly. This was fixed for upcoming 1.8.21121. So plain session management should now ensure that if the Konversation window was hidden on session end, it will also be restored as hidden on session restore on the next login now. Without session management, when registering Konversation for Autostart, at least with current 1.8.21120 it respects the flag and starts hidden. So closing as UPSTREAM issue, as this is an design flaw in the desktop environments when it comes to missing integration of autostart and session management. Current behaviour is the same as also seen with other single instance applications like KMail. So use autostart only if session management is disabled.