4 points
*
it can still look like this!
the oxygen theme still works fine on plasma 5 (and supports dark colourschemes)
3 points
3 points
just search your package manager for oxygen (it’s called a different thing in every distro)
you’ll want the icons (oxygen-icon-theme or similar), decorations (oxygen-window-decorations), and widget theme (oxygen-qt-theme). there might also be a meta package called kde-oxygen-theme or something with all 3
it only works on qt apps though, and the gtk oxygen theme is long abandoned