Comment # 8 on bug 913339 from Wolfgang Bauer

FYI, there is a general solution in sight:
http://blog.davidedmundson.co.uk/blog/xembed_back

In short that's a daemon that converts old-style (XEmbed) system tray icons to
the "new" system (well, it has been introduced in 2009 already...), and should
work with *any* application.

It's not released yet, but probably will be part of Plasma 5.5.

I created a package here if someone wants to try it:
http://download.opensuse.org/repositories/home:/wolfi323:/test/
Just install xembed-sni-proxy and logout/login (or reboot), it will be started
automatically.

It worked fine in a quick test (with a KDE3 and a Java application that both
didn't showup in the Plasma5 system tray before).
Only problem: the icons were a bit small compared to the others. But that's
exactly one of the main limitations of the old system and one of the reasons
why it got dropped/replaced. Not sure if this can be "fixed".

I do think we should get this into Leap before the release, and make sure it is
installed by default. Although an update to Plasma 5.5 shortly after the
release probably would be ok too (not sure what the plans are regarding
this...).

@stakanov: just to be clear: you need to enable the option "Show layout
indicator" in KDE's keyboard layout settings to have KDE's keyboard layout icon
in the system tray. The default is enabled (for more than one layout) though.

This should work fine, show the current layout and let you switch layouts. If
it doesn't work, it is a completely different bug anyway.

If you use some third party application for switching layouts, you might be
affected by the missing XEmbed support though. This should be fixed by
xembed-sni-proxy then.
You'd need to clarify this.