The update systray icon indicates that there are updates available (arrow with blue dot). Clicking it, bring the dropdown telling me there's 2 updates available. Clicking "Update" brings me to Discover, which say "No updates". I.e. systray notification daemon (?) isn't updating itself. Kubuntu 17.10 with backports, all latest updates installed.
*** This bug has been marked as a duplicate of bug 385754 ***
Actually, do you have the Flatpak backend installed?
Yes, I had Flatpack backend installed as these instructions (your's, if I'm not mistaken): https://pointieststick.wordpress.com/2018/01/13/flatpak-support-in-discover/ However the issue isn't present in my new 18.04 install, where I installed the backend via the button in Discover > Settings.
Yep, that's me. :) Does the issue disappear if you run `flatpak update` from the command line?
As mentioned in my previous comment, I'm currently running a new installation of Kubuntu 18.04 (completely wiped my 17.10 before installing), and so far I haven't experienced this particular isse. Which, unfortunately, leaves me unable to test your suggestion.
OK, re-duping to Bug 385754, then. *** This bug has been marked as a duplicate of bug 385754 ***
Seems I spoke too soon, kinda. I just now experienced it again, having the icon indicate updates, and the dropdown telling me that there were two updates available, though none were found either in Discover or by `sudo apt update` I ran `flatpak update` but the ghost updates persisted. It did however go away after I did some loggin-in-logging-out, though I did not pay attention to if it was gone after one, or several re-logs, as my purpose for the login-logout was something other than this issue. * Kubuntu 18.04, with installed Flatpak and Snap backend, via Discover > Settings buttons