It did not get far in market share, sure, but it never stopped going like Big Screen did and made the transition to 6 at the same time as Plasma Desktop.
Here are some recent developments:
1. https://plasma-mobile.org/2025/07/08/releases-25-07/
(also explaining that most software is part of 'Plasma Gear', which makes sense as it is software for both mobile and desktop, but has the downside of making Mobile less visible)
2. https://blogs.kde.org/2025/07/05/this-week-in-plasma-chuggin... and look for Plasma Keyboard in this post.
(Personally I am a bit sad that they are seemingly abandoning Maliit, which is also used in Sailfish OS and Ubuntu Touch and is IMHO fine, but hey, at least it shows that Mobile is not dead.)
I mean more like it didn't progress beyond prototype designs. It never felt polished or even close to nice looking. More like desktop Plasma UI minimized to touchscreen scenario, rather than significantly designed for it (like Sailfish). But good to see it's progressing too.