[thingie]

Is there some kind of how to that'd say 'buy this single device (that is actually widely available at retail for a reasonable price), install it in this way and you will have something to play with'?

[trotsky]

Speaking as a long time KDE user, having "the one true path" really isn't their style...

But they do have compatible devices:

http://community.kde.org/Plasma/Active/Devices

and installation instructions for a variety of builds:

http://community.kde.org/Plasma/Active/Installation

[malkia]

Only Intel Atom devices? No ARM? Mips?

[sho_hn]

Various people have Active in use on Tegra2 and other ARM kit (see YouTube for demos), but I'm not sure about ready-made images for them.