/etc/xdg/autostart/cinnamon-settings-daemon-media-keys.desktop is in cinnamon-settings-daemon 3.6.2-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 | [Desktop Entry]
Type=Application
Name=Cinnamon Settings Daemon - media-keys
Exec=/usr/lib/x86_64-linux-gnu/cinnamon-settings-daemon/csd-media-keys
OnlyShowIn=X-Cinnamon;
NoDisplay=true
X-GNOME-Autostart-Phase=Initialization
X-GNOME-Autostart-Notify=true
X-GNOME-AutoRestart=true
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