FocalUpgrades/Kubuntu
Before upgrading it is recommended that you read the release notes for Kubuntu 20.04 LTS, which document caveats and workarounds for known issues in this version. From 19.10, there may a delay of a few hrs to days between the official release announcements and the Ubuntu Release Team enabling upgrades.
https://help.ubuntu.com/community/FocalUpgrades/Kubuntu