Get Plasma Bigscreen
Plasma Bigscreen is not yet widely available.
We are planning to join the Plasma release schedule starting with Plasma 6.7 (in June), which will make it possible for distributions to ship it in their repositories.
In the meantime, there are some ways to test and try out Bigscreen, described below. Note that this is still in development, proceed at your own risk!
You can check the status of Plasma Bigscreen on the Matrix channel or the KDE Invent repository.
KDE Neon
KDE Neon has a development version of Plasma Bigscreen in its repositories. This image, based on KDE neon, can be tested on x86-64 based computers.
postmarketOS
PostmarketOS (pmOS) is a pre-configured Alpine Linux that can be installed on smartphones, SBC's and other mobile devices. View the device list to see the progress for supporting your device.
Plasma Bigscreen is currently only available in the nightly repository that tracks Plasma development. Follow the setup guide after installing pmOS regularly (ex. with Plasma Desktop).
Building it yourself
Developers use the kde-builder utility to build and develop Plasma Bigscreen on most distros (with reasonably new dependencies, like Arch and Fedora). See the wiki page on how to set this up.