Quick Google search for "Gnome Shell Pidgin SysTray" had a fair few hits on how to get a working icon back. So it would appear that Gnome also did remove support for Xembed, likely even before KDE did.

On Jul 24, 2015 01:20, "Eric Griffith" <egriffith92@gmail.com> wrote:

Don't have my laptop in front of me to confirm but my guess is no. Moving away from Xembed and dropping support for it in a too-be-decided future version of the desktop environments was announced in 2011 with the advent of Status Notifiers and libappindicator.

On Jul 24, 2015 01:12, "Reindl Harald" <h.reindl@thelounge.net> wrote:
does the same application work on the Fedora default desktop (GNOME)?
if the answer is yes KDE is to blame, period

Am 24.07.2015 um 06:59 schrieb Eric Griffith:
Reindl, I bash on a lot of design decision from the KDE and GNOME camps
alike, but this wasn't one of them. Xembed had to go, it was a design
nightmare. As far as who's fault it is.. I really gotta go with the apps
on this one. They had four -years- of warning that the "traditional"
xembed way of sys tray icons was going away eventually. If they couldnt
find time to port over to Status Notifiers / App Indicators by then that
that's their problem / or the project is dead anyway.

On Fri, Jul 24, 2015 at 12:44 AM, Reindl Harald <h.reindl@thelounge.net
<mailto:h.reindl@thelounge.net>> wrote:

    Am 24.07.2015 um 03:16 schrieb Markus Slopianka:

        On Thursday 23 July 2015 13:32:58 Emilio Recio wrote:

            Does anyone know of an app that can implement xembed feature?




            This is a major fail for KDE, IMNSHO.

        Wrong. It's a major fail for your applications

    strange attitude - if *non-kde* apps have problems with the systray
    and did not before KDE5 it's hardly a failure of the application,
    it's *again* a incompatible and ignorant regression as it happens
    every few years so that i even start asking myself "am i right in my
    mind to use linux desktop"

    "fail for your applications" - WTF - the world of application
    developers don't turn around KDE and broken desktops, i heard the
    same b**** with the over a year flickering control bar with KDE 4.0
    in combination with nvidia cards - the same - it worked befor
    KDE3->KDE4, so KDE is the problem and not the card and it's the job
    of a developer to handle it if it has worked before AND NO "it's
    free" don't justify carelessly while whine every year why linux
    desktops are a niche and how to change that

    if developers like linux desktops no longer be a niche the just need
    to stop user visible major changes and breaking things which worked
    and are in use - that's it, no Fedora.next, just don't break the
    user expierience once per year and you will stop lose existing ones
    and get new ones which no longer need to fear that their workflow
    get broken again and again

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