If everything goes well, the update to Fedora Kinoite 40 will be available in Plasma Discover once you update to tomorrow's Fedora Kinoite 39 update.
Note that we currently don't have proper download progress reporting in Discover's interface so please be patient while the update downloads. You can check "progress" via the network traffic in the network widget.
Stay tuned for incoming improvements to rpm-ostree support in Discover 🙂.
