the gnome-software based update notification in gnome is broken or flaky at
best. To verify I installed a fresh Leap on Friday, rebooted and let it sit
there with a user logged in until Sunday afternoon. No notification appeared
that an update is available. One has to manually run gnome software and even
press the button to manually refresh, otherwise it claims that there are no
updates.
After installing the first update, which is a package manager update (and a
useless forceful reboot) again gnome doesn't notify about additional updates. I
had to press refresh twice until it showed the updates.

This has to work out of the box!