You said that 3 months ago, in which time your primary competitors have all released a 3b+ image.
Yes, I have spent months playing with parameters. The default ones you link to are certainly not stable on a 250 frame. Increasing the gyro and accel filters helps, but there is still an uncontrollable wobble. Compass calibration is impossible to maintain, I assumed because of the close proximity of the power circuits. Once calibrated, it starts throwing errors a few mins later. (I've read all the articles I can find, and spent way too many hours of my life waving a drone in circles around my lounge. Pretty sure it shouldn't be this hard)
Motor calibration? Do you mean ESC? I've tried several different ESCs, SImonK and BLheli firmwares, calibration is fine using PWM, and everything seems to operate fine using Oneshot or Dshot as well. Which is another mystery in the config - your docs say PWM only is support, forum posts say only SimonK should be used, but ardupilot docs and posts everywhere say Oneshot is better. And it does seems to work.... so are your docs wrong? or out of date?
If you do actually mean "motor calibration" - That's a new one on me! How do I calibrate motors?
Don't have the pi to hand at the moment, but from memory - there was a GCS_bridge process , lots of Mavros processes, and a few others I didn't recognise. I understand that your systemd script is meant to disable the mavros service, but didn't appear to.
The software is the primary frustration, and the reason I gave up. I couldn't be sure if the drone was unstable because of the way I'd deployed the software, because of the 250 frame, or just because of my inexperience with building a quad. THere are plenty of guides and tutorials to learn about building, but there were zero answers as to how to deploy the software. I tried in my previous post, and you still haven't answered!
Could you please, please, just explain what is needed to run on the pi, and how the image differs from simply running the binary on raspbian. Even really simple config options such as enabling I2C, SPI, and hardware serial bus isn't documented anywhere.