I will do some necrobump here as this bug seems to be "almost resolved" and i didnt found any better bug report to include this.

So far Qt Virtual keyboard works, somehow, but with some issues, that kills the experience.

 - We either have enabled (autoshow) and disabled keyboard, but most of time i need to show keyboard on demand (and i guess this will be important for lot of tablet users), swipe from bottom gesture in gnome works well in this manner
 - Keyboard sometimes does not register input at all (cannot hide it, no letters are going into text field and so on
 - Autoshow only works in Qt apps
 - Keyboard uses 50% of the screen .. that wouldnt be issue as you can hide it, but there is no way to bring it back

You guys are close, dont give up, i would really love to get rid of the Gnome desktop on my PC :)

I'd say this bug is fixed with https://bugs.kde.org/show_bug.cgi?id=439911

If you're on Wayland, yeah. But that's the only place we formally support the Maliit virtual keyboard at this point anyway.

*** This bug has been marked as a duplicate of bug 439911 ***