OK,
Thanks for your answer.
When I tried to install gantt with GUI, it asked during installation if I want updates to be proposed. I guessed there should be a place where this choice is saved to avoid the update window to launch at startup for all users.
It’s usefull for me, because I don’t want users to install new versions, especially in their own account. I manage automatic updates by myself, after validating. This is how system-managers always work on professional/educational PCs. This is a condition to ensure PCs in a classroom are OK, and all students work on the same version (which is important, for exams, for example).
If not possible, I’ll keep this update window, but it’s really not a safe way for me.
Regards
E.T.