Ubuntu Budgie 18.04 LTS System Tray Icons not all showing

This problem is common for both Ubuntu 18.04 and Ubuntu Budgie 18.04.

The reason of issue is lack of the libgtk2-appindicator-perl package in main Ubuntu 18.04 repository. A workaround is to install libappindicator-dev:

sudo apt install libappindicator-dev

and Gtk2::AppIndicator perl extension:

sudo cpan -i Gtk2::AppIndicator

Restart your applications, now all of missing icons have to appear in system tray.

Here is the bug in Launchpad:

https://bugs.launchpad.net/ubuntu/+source/gnome-shell-extension-appindicator/+bug/1795121

It says 18.10, but I see exactly the same thing in 18.04. The workaround described in this works: Alt+F2, r, Enter (restarting the window manager).

An update to this: the issue was fixed and the fix released a while ago now. I haven't had the issue reoccur since.

Using budgie settings ensure you have the appindicator applet added to your panel.

A few applications show their panel icons as application indicator and not as a traditional system tray icon.