@JulianOes I started from scratch and I was able to build DronecodeSDK backend on host PC without issues. It looks like golang was missing as you pointed out.
However I still cannot connect DronecodeSDK backend running on host PC to jMAVSim running on docker container. I see your concerns regarding container networking but I'm able to connect QGC running on host PC to the simulator in container.
It looks like the backend is not able to connect to an autopilot running in a different machine, in my case:
1. DronecodeSDK backend 172.17.0.1
2. PX4 simulator (Firmware -> make posix jmavsim) 172.17.0.3
backend keeps showing messages:
No known remotes (udp_connection.cpp:130)
From the webinar it looks like you run everything on same IP (simulator, backend and python app)