Is Linux About SysTray?

No.

Desktop environments have removed or are removing support for the legacy GtkStatusIcon (aka system tray). However, there are many new, capable, cross-desktop APIs that replace the functionality previously provided by tray icons. Here you can find a list of replacement APIs and see how well-supported they are.

I want to…

CloudProviders

If you want to communicate synchronization status or provide actions related to cloud storage devices, you can use the CloudProviders DBus API

GNOME KDE MATE Pantheon Ubuntu Xfce
Status Icon ✔️ ✖️ ✖️ ✔️ ✔️ ✖️
Actions ✔️ ✖️ ✖️ ✔️ ✔️ ✖️

Desktop Actions

If you want to provide quick access to common actions, you can add them to your .desktop file

GNOME KDE MATE Pantheon Ubuntu Xfce
Actions ✔️ ✔️ ✔️ ✔️ ✔️ ✔️
Icons ✖️ ✔️ ✔️ 🗋 ✖️ ✔️

Launcher Entry

If you want to communicate progress information for long-running background tasks or the number of items needing action in your app (such as tasks or messages) you can use the LauncherEntry DBus API

GNOME KDE MATE Pantheon Ubuntu Xfce
Progress Bar ✖️ ✖️ ✖️ ✔️ ✔️ ✖️
Badge ✖️ ✖️ ✖️ ✔️ ✔️ ✖️

MPRIS

If you want the user to be able to access media player controls for you app, you can listen to and supply information to MPRIS

GNOME KDE MATE Pantheon Ubuntu Xfce
Media Info ✔️ ✔️ ✔️ ✔️ ✔️ ✔️
Player Controls ✔️ ✔️ ✔️ ✔️ ✔️ ✔️
Album Art ✔️ ✔️ ✔️ ✔️ ✔️ ✖️

Notifications

If you want to alert the user that something has changed in your app, you can send a notification bubble

GNOME KDE MATE Pantheon Ubuntu Xfce
Bubbles ✔️ ✔️ ✔️ ✔️ ✔️ ✔️
Actions ✔️ ✔️ 🗋 ✔️
Notification Center ✔️ ✔️ ✖️ ✔️ ✔️ ✔️
Images ✔️ unknown ✔️ ✔️ ✔️ ✔️
Replace ✔️ unknown ✖️ ✔️ ✔️ ✔️

Portals

XDG Desktop Portals are sandbox-compatible DBus APIs for accessing system functions. Desktop environments can use these portals to request consent from users and provide an ongoing visual indication of portal usage.

Location

The Location Portal is responsible for providing apps with the device’s current physical location.

GNOME KDE MATE Pantheon Ubuntu Xfce
Consent ✔️ unknown unknown 🗋 ✔️ unknown
Indication ✔️ unknown ✖️ 🗋 ✔️ ✖️

Screencast/Recording

The Screencast Portal is responsible for providing apps with the display’s or a window’s visible content i.e. for recording, streaming, or remote viewing.

GNOME KDE MATE Pantheon Ubuntu Xfce
Consent ✔️ ✔️ unknown 🗋 ✔️ unknown
Indication ✔️ unknown ✖️ 🗋 ✔️ ✖️