As of right now, Plasma Bigscreen isn't available for public use yet. This is due to not being developed for so long. The project has been revived, but it might take a while until it becomes stable and is available for public use.

Missed opportunity to call it KDE Media Center

Personally, I just want an open-source drop in replacement for Chromecast.

Idk what it is about Kirigami. But it somehow looks very retro and dated, but more modern than any other design system at the same time.