The tools are WIP, documentation is perfectible to say the least, but the main point is that a sneaky guy dubbed 'WideOpen' (certainly a pun on the fact the headunits targetted in our cars are Std5Wide models, LG built) managed to find his way in. Now that it's done, it seems easy from afar, but hey, you had to find in the first place and that wasn't straightforward.
I will publish my findings overtime
Surprisingly enough, the headunit IS NOT a glorified android tablet !
It's an Intel based computer with a few proprietary devices.
OpenEmbedded built Linux (with remnants of a redhat flavor)
QT5+QtQuick/QML based apps
Versions in Unit mentions QT 5.4, but image ressources vastly use ASTC encoded PNG's which are possible since 5.13 (ASTC are texture files used by the egl/opengl graph scene engine that are more lightweight to process)
Extensive use of DBus signaling