KDE devs have been quietly working on Plasma Keyboard, a new on-screen keyboard for desktop and mobile part of the “We Care About Your Input” KDE Goals initiative. Although not ready for texting yet, it has been making progress. Hopefully it’ll be in a screen near you soon. Join the effort!
https://invent.kde.org/plasma/plasma-keyboard
This is a great initiative! I tried plasma on a tablet like device a while ago and the keyboard was one of the main issues holding it back.