I have opened the C++ demo project https://github.com/FelgoSDK/Demos-Examples/tree/master/appdemos/cpp-qml-integration , did the described changes to use the live client module with custom C++ code (edited build config and main cpp), built and ran the application, and the output I get is:
ML debugging is enabled. Only use this in a safe environment.
MyGlobalObject doSomething called with “TEXT FROM C++”
Cannot mix incompatible Qt library (5.15.2) with this library (5.15.7)
I am using the Felgo 5.12.2 kit that was shipped with the installer. On Manjaro Linux, I do have Qt 5.15.7 and Qt 6.4.1 installed through system package manager. However, the Qt5 and Qt6 kits are not even enabled in the project, so I struggle to understand how the 5.15.7 files are even picked up. I am also running the QtCreator that was shipped with Felgo. Obviously, I tried cleaning the project, rerunning qmake, rebuilding, etc. Therefore, I am out of ideas.
If you happen to have an Arch Linux or a Manjaro Linux installation, please see if you can reproduce the issue with Qt 5 packages present on the system via pacman. It seems like due to the fact that the system Qt 5 is in the PATH, it may somehow sometimes shadow the Felgo version, even though I checked that Felgo kit is pointing to the right qmake executable, as well as the detailed view of all the kit’s variables.