KDE Plasma 5

KDE Plasma 5 is the fifth and current generation of the graphical workspaces environment created by KDE primarily for Linux systems. KDE Plasma 5 is the successor of KDE Plasma 4 and was first released on 15 July 2014. It includes a new default theme, known as "Breeze", as well as increased convergence across different devices. The graphical interface was fully migrated to QML, which uses OpenGL for hardware acceleration, which resulted in better performance and reduced power consumption.
Overview.
Software architecture.
KDE Plasma 5 is built using Qt 5 and KDE Frameworks 5, predominantly plasma-framework.
It improves support for HiDPI displays and ships a convergable graphical shell, which can adjust itself according to the device in use. 5.0 also includes a new default theme, dubbed Breeze. Qt 5's QtQuick 2 uses a hardware-accelerated OpenGL(ES) scene graph (canvas) to compose and render graphics on the screen, which allows for the offloading of computationally expensive graphics rendering tasks onto the GPU, freeing up resources on the system's main CPU.
Windowing systems.
KDE Plasma 5.0 uses the X Window System. Support for Wayland was prepared in the compositor and planned for a later release. It was made initially available in the 5.4 release. Stable support for a basic Wayland session was provided in the 5.5 release (December 2015).
Support for NVIDIA proprietary driver for Plasma on Wayland was added in the 5.16 release (June 2019).
Development.
Since the split of the KDE Software Compilation into KDE Plasma, KDE Frameworks and KDE Applications, each subproject can develop at its own pace. KDE Plasma 5 is on its own release schedule, with feature releases every three-to-four months, and bugfix releases in the intervening months.
Linux distributions using Plasma.
Plasma 5 is a default desktop environment (or one of the defaults) on Linux distributions, such as: 
Plasma Mobile.
Plasma Mobile is a Plasma variant for smartphones. It is currently available for the Nexus 5 and Nexus 5X, supported devices on postmarketOS, and the PinePhone.
After Plasma Active sponsor Coherent Theory (under the Make·Play·Live brand) had given up their ambitions to release a tablet computer, Blue Systems emerged as new sponsor and shifted the focus of Plasma's handheld work towards smartphones.
The official announcement of the new form-factor interface was on 25 July 2015 at Akademy, accompanied by a working prototype running on a Nexus 5. Plasma Mobile runs on Wayland and it is compatible with Ubuntu Touch applications. While not a priority, Android application support through Anbox could eventually come to the OS.
PinePhone - KDE Community Edition was made available as pre-orders on 1 December 2020.
History.
The first Technology Preview of Plasma 5 (at that time called "Plasma 2") was released on 13 December 2013. On 15 July 2014, the first release version Plasma 5.0 saw the light of day.
In spring 2015, Plasma 5 replaced Plasma 4 in many popular distributions, such as Fedora 22, Kubuntu 15.04, and openSUSE Tumbleweed.
Releases.
Feature releases are released every four months (up to 5.8 every three months) and bugfix releases in the intervening months. Following version 5.8 LTS KDE plans to support each new LTS version for 18 months with bug fixes, while new regular releases will see feature improvements.
Future Planning.
Plasma 6: According to the official schedule, "Following 5.18 LTS, our next Plasma 5 LTS will likely be at the same time as the first Plasma 6 release, no date has been set yet".