From openQA testing, it seems that from Fedora-Rawhide-20231226.n.0 onwards, we do not get update notifications in KDE. openQA has a test where it boots to a console, prepares the system such that an update is definitely available, then runs the desktop, waits ten minutes, and expects a notification to become visible during that time. That test was passing fine up to and including Fedora-Rawhide-20231225.n.0 , but has failed every day since then on KDE. Looking at the screenshots and video from the test, nothing resembling an 'update available' notification ever seems to appear in the panel during the ten minutes the test waits. It seems like the KDE Frameworks 5.247.0 KDE Plasma 5.91.0 KDE Gear 24.01.85 megaupdate landed in that compose - https://bodhi.fedoraproject.org/updates/FEDORA-2023-c0c2667cdd . With that many packages I'm not sure what would be responsible for this, so filing against Discover for now.
Proposing as a Final blocker as a violation of https://fedoraproject.org/wiki/Fedora_40_Final_Release_Criteria#Update_notification - "Release-blocking desktops must notify the user of available updates, but must not do so when running as a live image" (this is the 'installed system' case).
FEDORA-2024-252041c245 has been submitted as an update to Fedora 40. https://bodhi.fedoraproject.org/updates/FEDORA-2024-252041c245
FEDORA-2024-252041c245 has been pushed to the Fedora 40 stable repository. If problem still persists, please make note of it in this bug report.