I often install packages and updates for them, although sometimes it is not convenient to do a reboot if one of the packages needs it, so is there any way of telling BEFORE installing the package/update whether or not it will require you to do a reboot? I have already looked here and the solutions there don't solve my problem, nor the more or less same one described there.
There's no flag of sorts on packages that indicate that a reboot is required if the package is installed or updated. So, short answer: you can't.
However, you could extract the .deb files of the package before installing or updating to see if a reboot notification is made in the