VirtualKeyboard not working on Wayland without libkxbcommon

Full history available on qt-interest ML:
https://lists.qt-project.org/pipermail/interest/2018-October/031352.html
https://lists.qt-project.org/pipermail/interest/2018-October/031353.html
https://lists.qt-project.org/pipermail/interest/2018-October/031368.html

Qt: 5.11.1, custom built for arm A9 (imx61 board).

Summary:
Following http://doc.qt.io/qt-5/qtvirtualkeyboard-deployment-guide.html#using-qt-virtual-keyboard-with-qt-wayland, it works on Linux Desktop (wayland over X) but not on embedded Linux (linuxfb).

Enabling Qt and Wayland debug, I can see this log on the compositor side, when i hit a key of the virtual keyboard:

qt.virtualkeyboard: InputContext::::sendKeyClick(): 16777219
[2541671.231] -> zwp_text_input_v2 at 14.keysym(0, 0, 1, 0)
[2541671.480] -> zwp_text_input_v2 at 14.keysym(0, 0, 0, 0)

Virtual keyboard send a "key click" with code 16777219, wayland's zwp_text_input_v2 says that the key code is zero.

On the client side, all QKey*Event have both key and native code set to zero.

QtWayland seats b/w the virtualkeyboard and libwayland-server, looking at

/home/chgans/Projects/qt5/qtwayland/src/compositor/extensions/qwaylandtextinput.cpp
/home/chgans/Projects/qt5/qtwayland/src/client/qwaylandinputcontext.cpp
/home/chgans/Projects/qt5/qtwayland/src/shared/qwaylandxkb.cpp

It seems that on system without xkbcommon, the handling of keys is bogus and/or incomplete. Or i have misconfigured my Qt build or I have a weird runtime issue.

Is the Qt virtual keyboard supposed to work with QtWayland and linuxfb QPA?