When I log in on my laptop running Kubuntu with the Neon repositories, the default icons (network manager, battery, etc.) don't appear in the system tray (nor in the menu next to it containing the hidden items). Furthermore, they also don't show up in the "Entries" page of the system tray settings window. I was looking through the logs, and this looks like it might be relevant: file:///usr/share/plasma/plasmoids/org.kde.plasma.private.systemtray/contents/ui/items/AbstractItem.qml:27: TypeError: Cannot read property 'top' of null I get one of those lines in my logs each time I log in. Reproducible: Always Laptop is running Kubuntu 15.10 with KDE Neon repositories.
Scratch that, after upgrading to today's batch of Neon packages it looks like this has been resolved. Seems like it was a temporary issue.