https://www.kde.org/announcements/kde-p ... ibrem5.php
On hn: https://news.ycombinator.com/item?id=15248260 with dev reacting.

Indeed, the article gives hope. But I’m afraid, that a running Plasma Mobile OS will be available only for and only when the Libre5 phone will be released. I’m very interested in this OS as a base system for a serious product development like Purism, but I can evaluate the OS on the reference device Nexus 5X. The installation fails. Therefore I think, currently no one is working on the OS currently.

Therefore I think, currently no one is working on the OS currently.

That is not true.
Though my Nexus 5 broke I saw people having Nexus 5X running with Plasma Mobile and development is still going on.

I have evaluated Plasma Mobile in September this year. I was able to install the software on a Google Nexus 5x, but the software wasn't running as expected: No phone features and even not network features at all. I could just open some settings and basic application like a clock. Has someone installed Plasma Mobile successfully like demonstrated in the promotion video?