Hi everyone,
My system is up to date but the Discover notification on system tray keeps show that there is one update available, I've try to update it using pkcon and also to reinstall Discover but nothing change.
I can't get rid of this notification.
Did anyone knows if there is any cache files from Discover that may cause this bug?

I tried to purge Discover, reboot and install it again. Didn't work.

It has been mentioned problem has been fixed in Plasma 5.16 due out on June 11 if schedules are met. https://community.kde.org/Schedules/Plasma_5
I have not seen the problem in my use of KDE Neon Testing Edition so my guess is it is fixed. You just have to wait a few daze.

Thanks,
It was fixed on Plasma 5.16 indeed.