If you're on wayland, it's not going to work, which is a deliberate gtk/wayland design decision. We should probably disable the virt-manager option in that case.

Upstream now:

commit 147a3b4790b9c7bf47271a01f23ef08aa527479d (HEAD -> master)
Author: Cole Robinson <crobinso>
Date:   Fri Jun 14 20:04:35 2019 -0400

    preferences: Disable systray option if we know it won't work
    
    Basically on wayland, if appindicator isn't available
    
    https://bugzilla.redhat.com/show_bug.cgi?id=1666597

Try to verify this bug with build:
virt-manager-2.2.1-1.el8.noarch
virt-install-2.2.1-1.el8.noarch
libvirt-4.5.0-24.module+el8.1.0+3205+41ff0a42.x86_64
qemu-kvm-2.12.0-77.module+el8.1.0+3382+49219945.x86_64

Steps:
Scenario-1 Select Standard(Wayland display server) when you login rhel8 system

# echo $XDG_SESSION_TYPE
wayland

1.1 Launch virt-manager: #virt-manager
1.2 Click on one connection.
1.3 Click Edit->Preferences.
1.4 Go to General tab, and check 'Enable system tray icon' status.

Result: systray option is disabled, and when you move the cursor to on it, it shows "No appindicator listener found, which is required on wayland.", it's as expected.


Scenario-2 Select Classic(X11 display server)

# echo $XDG_SESSION_TYPE
x11

2.1 Launch virt-manager: #virt-manager
2.2 Click on one connection.
2.3 Click Edit->Preferences.
2.4 Go to General tab, and check 'Enable system tray icon' status.
-Result: systray option is enable by default, and virtual machine manager icon appears in the bottom right corner of the navigation bar.
2.5 Uncheck Enable system tray icon.
-Result: virtual machine manager icon disappear, it's as expected.


Scenario-3 Select Classic(Wayland display server)
Result: Get same result with Scenario-1

Scenario-4 Select Custom
# echo $XDG_SESSION_TYPE
x11

Result: But there is no virtual machine manager icon appears in the bottom right corner of the navigation bar when I check on "Enable system tray icon".

Scenario-5 Select Standard(X11 display server) on Xorg
Result: Get same result with Scenario-4

Hi Pavel, 
From testing Scenario-1 to Scenario-3, i get expected results, so please help me have a look of Scenario-4 and Scenario-5, i don't why systray option doesn't work, thanks.

Hi Pavel,
Please help me have a look of Comment 4 issue, thanks.
Do we need cover such scenarios while we verify this bug?

BR,
juzhou.

Hi Junqin,

I was investigating the issue since yesterday.  So far I've come to the state that
in all the Scenario-2, Scenario-4 and Scenario-5 (X11 sessions) the systray is there
but for some reason the icon is invisible, but if I click the area where the icon shoul
appear it works.  If I lock the screen and unlock it in all of the X11 scenarios the
systray icon appears.  I'm testing it in VM, I'll try to test it on real HW as well
and I'll try to debug the issue why the icon is not there since beginning.

I'm not sure whether we need to cover all scenarios as I don't know what is supported
but all of them are mentioned in our documentation [1].

[1] <https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/8/html/considerations_in_adopting_rhel_8/desktop-and-graphics_considerations-in-adopting-rhel-8>

I've done a bit more testing and research and it looks like that the "missing" icon in systray
might be issue in gnome-shell-extensions component as it provides gnome-shell-extension-top-icons
package.

This is how it works in my RHEL-8 installation:

1. Make sure that "Enable system tray icon" is enabled and quit virt-manager.

2. Start virt-manager again, there is no visible icon on the right side of system tray
   but if I click to the place where it should be it will hide/show virt-manager window.

3. In virt-manager go to "Edit->Preferences", disable and enable the "Enable system tray icon"
   again and now the icon will appear in system tray.

4. Now that the icon is visible quit virt-manager and start it again and the icon will be
   again "invisible" but still clickable.

This happens for all X11 sessions.


The conclusion:

On wayland the systray icon will not work.  On X11 it should work but there seems to be a bug
in gnome-shell-extensions which provides gnome-shell-extension-top-icons.  I've tried it with
pidgin which adds itself into system tray as well and it behaves the same that the icon is there
but invisible.

This bug can be verified by checking that on wayland the "Enable system tray icon" is not clickable
and tooltip explains why and another bug should be open to track the gnome-shell-extensions issue.

Thanks for Pavel's investigation, i file a new bug 1746372 to track the gnome-shell-extensions issue.
And move this bug from ON_QA to VERIFIED status, thanks.

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHSA-2019:3464