7
On-screen keyboard
(lemmy.ca)
KDE is an international technology team creating user-friendly free and open source software for desktop and portable computing. KDE's software runs on GNU/Linux, BSD and other operating systems, including Windows.
Anything that isn't a native KDE app. Chromium, Firefox, OnlyOffice, Libre office, Gimp, Inkscape, etc...
Literally only KDEs own apps actually bring up the keyboard.
Do you have any input method related environment variables set?
Nope and nope.