Kubuntu 18.10 Cosmic Cuttlefish was released on October 18th 2018 with 9 months support. As of 18th July 2019, 18.10 reaches ‘end of life’. No more package updates will be accepted to 18.10, and it will be archived to old-releases.ubuntu.com in the coming weeks.
The official end of life announcement for Ubuntu as a whole can be found here [1].
Kubuntu 19.04 Disco Dingo continues to be supported, receiving security and high-impact bugfix updates until January 2020.
Users of 18.10 can follow the Kubuntu 18.10 to 19.04 Upgrade [2] instructions.
Should for some reason your upgrade be delayed, and you find that the 18.10 repositories have been archived to old-releases.ubuntu.com, instructions to perform a EOL Upgrade can be found on the Ubuntu wiki [3].
Thank you for using Kubuntu 18.10 Cosmic Cuttlefish.
The Kubuntu team.
[1] – https://lists.ubuntu.com/archives/ubuntu-announce/2019-July/000247.html
[2] – https://help.ubuntu.com/community/DiscoUpgrades/Kubuntu
[3] – https://help.ubuntu.com/community/EOLUpgrades