I would like to install the current 3.5 beta on my quad, but APM Planner only shows the stable release for Quad frame types. It shows the beta for traditional helicopters…but that seems to clearly be the wrong firmware.
So, it looks like the answer was ArduCopter-v2.px4, which I was able to install using the “custom” option. Still curious why APM Planner doesn’t show the beta firmware for anything other than helis.