The release announcement detailing the new features and improvements in Plasma 5.16 can be found here

Released along with this new version of Plasma is an update to KDE Frameworks 5.58. (5.59 will soon be in testing for Eoan 19.10 and may follow in the next few weeks.)

To upgrade:

Add the following repository to your software sources list:

ppa:kubuntu-ppa/backports

or if it is already added, the updates should become available via your preferred update method.

The PPA can be added manually in the Konsole terminal with the command:

sudo add-apt-repository ppa:kubuntu-ppa/backports

and packages then updated with

sudo apt update
sudo apt full-upgrade

IMPORTANT

Please note that more bugfix releases are scheduled by KDE for Plasma 5.16, so while we feel these backports will be beneficial to enthusiastic adopters, users wanting to use a Plasma release with more stabilisation/bugfixes ‘baked in’ may find it advisable to stay with Plasma 5.15 as included in the original 19.04 Disco release.

Issues with Plasma itself can be reported on the KDE bugtracker [1]. In the case of packaging or other issues, please provide feedback on our mailing list [2], IRC [3], and/or file a bug against our PPA packages [4].

1. KDE bugtracker: https://bugs.kde.org
2. Kubuntu-devel mailing list: https://lists.ubuntu.com/mailman/listinfo/kubuntu-devel
3. Kubuntu IRC channels: #kubuntu & #kubuntu-devel on irc.freenode.net
4. Kubuntu ppa bugs: https://bugs.launchpad.net/kubuntu-ppa

Code-named “Disco Dingo”, Kubuntu 19.04 continues our proud tradition of integrating the latest and greatest open source technologies into a high-quality, easy-to-use Linux distribution.

The team has been hard at work through this cycle, introducing new features and fixing bugs.

Under the hood, there have been updates to many core packages, including a new 5.00-based kernel, Qt 5.12, KDE Frameworks 5.56, Plasma 5.15.4, and KDE Applications 18.12.3

Kubuntu has seen some exciting improvements, with newer versions of Qt, updates to major packages like Krita, Kdeconnect, Kstars, Latte-dock, Firefox and LibreOffice, and stability improvements to KDE Plasma.

For a list of other application updates, upgrading notes and known bugs be sure to read our release notes:

https://wiki.ubuntu.com/DiscoDingo/ReleaseNotes/Kubuntu

Download 19.04 or read about how to upgrade from 18.10.

The beta of Disco Dingo (to become 19.04) has now been released, and is available for download at http://cdimage.ubuntu.com/kubuntu/releases/19.04/beta/

This milestone features images for Kubuntu and other Ubuntu flavours.

Pre-releases of the Disco Dingo are not encouraged for:

* Anyone needing a stable system
* Anyone who is not comfortable running into occasional, even frequent breakage.

They are, however, recommended for:

* Ubuntu flavor developers
* Those who want to help in testing, reporting, and fixing bugs as we work towards getting this release ready.
* the Beta includes some software updates that are ready for broader testing. However, it is an early set of images, so you should expect some bugs.

You can:

Read more information about the Kubuntu 19.04 Beta: https://wiki.ubuntu.com/DiscoDingo/Beta/Kubuntu

Download the Kubuntu 19.04 Beta images

Read the full text of the main Ubuntu Cosmic Beta announcement:

https://lists.ubuntu.com/archives/ubuntu-release/2019-March/004743.html

The Ubuntu Cosmic Release notes will give more details of changes to the Ubuntu base: https://wiki.ubuntu.com/DiscoDingo/ReleaseNotes