On recent TW, the invocation of ibus on KDE or other DEs seems broken.  The
ibus icon doesn't appear on the task bar, and it doesn't work on GTK2
applications like Firefox (while it seems working on GTK3).

The culprit is the race of ibus invocation at session start.  This has been a
long known problem, but some change in other components seems triggering the
issue more clearly now.

The fix is to delay the invocation of ibus via XDG autostart, as long as the DE
supports it.  We had a similar problem with fcitx, and it got fixed in that
way.

For DEs that don't support autostart, just putting some delay before starting
ibus daemon should suffice practically.