Universal_Robots_ROS_Driver VS ardupilot

They have a section for developer about ROS UR ROS

This is the Ros driver for ur-e series robot. You can simply follow the readme to setup a simulation involving a rviz model and some.basic planning and associated visualisation.

That’s not windows. It uses ROS

Oh no, really? I'm following the directions of this GitHub page which includes features such as "Realtime-enabled communication structure to robustly cope with the 2ms cycle time of the e-Series. " and then says, "To make sure that robot control isn't affected by system latencies, it is highly recommended to use a real-time kernel with the system."

They are widely used in narrow circles :)

Two of (arguably the best) open source RC aircraft flight controllers (ArduPilot and PX4) are using extended Kalman filters in their state estimators (essentially sensor fusion that provides attitude/position estimate):

https://github.com/ArduPilot/ardupilot/tree/master/libraries...

https://github.com/PX4/PX4-Autopilot/blob/main/src/modules/e...

I'm not that familiar with cleanflight/betaflight/inav scene to know what the FPV racer flight controllers use.

2. https://ardupilot.org/

Trimble also has some nice stuff, I think the BD940 is interesting. I do not know if it's recommended or not, but Ardupilot has a driver for the Septentrio GPS (https://github.com/ArduPilot/ardupilot/blob/master/libraries/AP_GPS/AP_GPS_SBF.cpp), as well for Trimble GPS (https://github.com/ArduPilot/ardupilot/blob/master/libraries/AP_GPS/AP_GPS_GSOF.cpp). So people have used these brands for drones.

For programmable open source autopilot: Arduino > Ardupilot (https://ardupilot.org).

You might also want to look at something like Ardupilot

I'd like to emphasize the reference to Ardupilot bc there is a lot of material already developed there: a lot about navigation and guidance from UAVs, and the low-level stuff. Check this out