Hi all,
I have been building PteroSim, a UE5 based simulator that runs JSBSim 6-DOF dynamics and connects to PX4 SITL. It is at open beta now and I am after feedback from people who work in PX4 SITL daily 
License upfront so nobody wastes time: PteroSim is proprietary, free for personal, academic and non-commercial use, paid for commercial use. PX4 is not bundled, you point it at your own build.
Connecting it: spawn an aircraft in PteroSim, select PX4 as the control source, then run
PX4_SIM_HOSTNAME=<ip> PX4_LOCKSTEP=1 PX4_SIM_SPEED_FACTOR=1 make px4_sitl none_iris
Lockstep engages once PX4 connects, so a run is repeatable instead of depending on how loaded the machine is. Here is what that looks like running:
What I built it for is work where the rendered world matters: camera, terrain following, visual navigation. Aircraft types the engine handles are multirotor, fixed wing, VTOL, helicopter and tailsitter, though the free build ships one of them, an F450 quad.
The sensor side covers the non-GPU set PX4 needs to fly, IMU, magnetometer, barometer and GPS, plus camera. There is a Python API over gRPC for scripted and headless runs.
Honest limitations at this stage: generic radar and lidar models are still being worked on, so if your loop depends on either, this is not ready for you yet. Free sessions are also capped at two hours with a cooldown after. That is enough to tell whether the bridge and the dynamics behave on your machine, and not enough to run a regression suite. If you want to hammer it in CI, say so and we will sort something out. Builds are Linux and Windows only, no macOS.
Docs, including the PX4 SITL page: SITL simulation with PX4 — PteroSim documentation
What would help me most: run the F450 against your own PX4 build and tell me where the bridge breaks. And if you want to see your own airframe in there instead of a stock quad, tell me what you are flying.