Docker SITL and Mavproxy not working with gazebo

Hi,
I use an ARM macbook

I am trying to run:

  1. sim_vehicle.py in a Docker container, exposing port 5760
  2. mavproxy on the host, using nix package, with --master=tcp:127.0.0.1:5760 --out=udp:127.0.0.1:14550
  3. gazebo harmonic on the host, installed with brew. One terminal for the server, one for the ui (gz sim -v4 -s iris_runway.sdf and gz sim -v4 -g)
  4. ardupilot_gazebo is compiled on the host, with the commands given in the repo
  5. QGroundcontrol

Running a non-gazebo model on sim_vehicle.py works: QGroundcontrol sees the drone connect and I can use it normally.

Running gazebo on its own works, I can see the runway and drone and can look around.

Running sim_vehicle.py with --vehicle gazebo-iris and/or --model JSON makes mavproxy fail to connect (it reports link 1 down and nothing further happens), so QGroundcontrol also doesn’t get a connection.

Is it a problem that the sim_vehicle.py runs in the docker container, without ardupilot_gazebo present/configured? Am I missing something major?