Hello. I'm running openbox with some KDE apps. After upgrading plasma-workspace and related packages from 5.9 to 5.10 many regular actions happen with a ~20 seconds delay, e.g. confirmation dialogues in dolphin appear with this delay, konsole displays tab completion results with this delay, cmst starts with this delay, etc. Apparently I'm not the only one affected, check 'see also'. .local/share/sddm/xorg-session.log is full of "Unexpected reply signature: got \"\", expected \"a{sv}\"" messages. I'm ready to provide more info if needed. This is a very annoying behaviour, it would be nice if you could fix it.
*** This bug has been marked as a duplicate of bug 382444 ***