Please provide a minimal, compilable example of your problem. Check it with a recent Qt6 version and if the issue still exists, create a bug report (or post it here and I'll take a look on it).

@starkm42 Thanks for the reply, the issue was to do with the fact mosquitto was compiled with a different library. To avoid this I am just going to run a ubuntu VM Thanks everyone for the help.

Ok, just to finalize this. Instead of the cmake code I attached above to link FFmpeg libraries, I used the same FindFFmpeg.cmake file that used by OBS Studio project on GitHub, and it worked as expected!

I don't know what is the difference yet, I need to read through it carefully and find the differences.

Can the MongoDB dlls be found at run time ?

Just to summerise the issue in case anyone else will be encounter something similar.

I want to use <execution> header from C++17 with GCC9 That requires Intel's TBB library and includes Both Qt and TBB use emit that is replaced by Qt. To solve this locally, I've undefined "emit" before using <execution> header. The general solution is to use -DQT_NO_KEYWORDS and replace emit/signal with Q_SIGNALS/ Q_SLOTS gcc9 uses task class from TBB that was deprecated in 2020. The solution is to use TBB 2019 or a newer GCC.

Thanks much all of the repliers.