/etc/xdg/autostart/gnome-welcome-tour.desktop is in gnome-initial-setup 3.28.0-2ubuntu6.
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 | [Desktop Entry]
Type=Application
Name=Welcome
Exec=/usr/lib/gnome-initial-setup/gnome-welcome-tour
AutostartCondition=if-exists run-welcome-tour
OnlyShowIn=GNOME;
NoDisplay=true
X-Ubuntu-Gettext-Domain=gnome-initial-setup
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