Cursor keys do not work as expected. On a Ubuntu system, running XFCE4 over VNC. With Kate and other KDE apps which have an editor component (e.g. Kile) the normal (separate) cursor keys do not work properly (using a standard UK 105 keys keyboard, the cursor keys work just fine in all other applications like vi, gedit, pycharm, netbeans chrome etc.) The up, right, left cursor keys from the inverted-T shaped keys do not work at all, the down key inserts new lines instead of scrolling down. The PgUp/PgDown, Home/End and Delete keys are also ignored. If the numeric keypad has numlock switched off, the cursor keys there work fine.
Ubuntu version 18.04 LTS (x86 64 bit architecture)
I think this is an upstream Qt issue that got fixed in up-to-date Qt versions. (perhaps there is some workaround, see below linked Qt bug) https://bugreports.qt.io/browse/QTBUG-44938