Where did the status icons go in GNOME 3.26.x and what can I do to bring them back?
The legacy tray was removed in 3.26 (it was a stop-gap measure, destined to be removed at some point, as explained in the corresponding bug). This is also mentioned in the release notes.
To see your indicator icons, you can use an extension such as TopIcons Plus.
There are multiple ways how to bring tray icons back.
AppIndicator Support
The way I use and I would recommend to you is the appindicator-support Gnome extension. There are multiple implementations:
KStatusNotifierItem/AppIndicator Support - The default one and the best way for beginners. It may be already preinstalled on some linux distributions.
[email protected] - Patched version of the previous one (I use this one). It is not distributed in extensions store so you have to download, extract and place it manually into
~/.local/share/gnome-shell/extensions/. But it offers a lot of configuration options.Zorin KStatusNotifierItem/AppIndicator Support - The fork of the first one. There is no big difference except reduced spaces between icons.
Each of these solutions also offers great integration into gnome-shell as it uses default dropdowns.
TopIcons
Another approach to bring tray icons back is TopIcons family of extensions. It all started with (no longer functional today) TopIcons extension.
TopIconsFix - Fixed version of TopIcons. It doesn't provide configuration and icons are too large to look nice. I don't very recommend this one.
TopIcons Plus - (The one on screenshot) This is a good extension. Provides configuration and icons look nice.
TopIcons Redux - Rewritten fork of TopIcons Plus. It may not work in the newest version of Gnome-shell.
Note: Keep in mind you may not be able to get all your tray icons working with TopIcons extensions.
Additions
Some programs with non-working tray icons can be fixed by changing the environmental variable XDG_CURRENT_DESKTOP before launching them. Try to change this variable to Unity or KDE. Test your program with the following commands:
XDG_CURRENT_DESKTOP=Unity programXDG_CURRENT_DESKTOP=KDE program
If one of the commands work, you can edit .desktop file of your program in ~/.local/share/applications/ or /usr/share/applications/ to include this environmental variable in Exec= parameter.
Exec=env XDG_CURRENT_DESKTOP=KDE program
Some users may be looking into a way to customize their tray icons to look united and to match the system icon theme (as on my screenshots above). In that case, take a look at Hardcode-Tray project.