If Boeing can't make the Max work without crashes, what makes you think a completely new supersonic aircraft can use a fork of Ardupilot with a few minor extras for supersonic flight?
Supersonic flight has much less overlap with subsonic flight than you might think. There are compression and twisting forces on the fuselage and flight surfaces which have no analog in conventional airliners.
And you can't just take the flight characteristics of one shape/size of aircraft and tweak them a little for your new design.
'If X can't do it...' is a bad argument that doesn't take any consideration of real life.
Just because they are a huge company with big spending power does not make it impossible for their codebases to be a pile of hot steaming garbage that even the best engineers struggle with.
Either way, your rebuttal about Boeing doesn't address the fundamental differences between control of a traditional aircraft-- which is all that any existing software can handle-- and control of a fundamentally different type of aircraft.
> Supersonic flight has much less overlap with subsonic flight than you might think.
And every supersonic aircraft also has to fly subsonic. So you really need two sets of software in a supersonic aircraft. Or more accurately three, because the transonic regime is weird enough to be its own thing.
What about the airplane given in the original example, the F-100, whose design predated the integrated circuit by something like a decade? Presumably control software improves stability, but otherwise the aircraft behaves in a predictable manner above and below Mach 1 as supersonic control software is a relatively recent addition.
Supersonic flight has much less overlap with subsonic flight than you might think. There are compression and twisting forces on the fuselage and flight surfaces which have no analog in conventional airliners.
And you can't just take the flight characteristics of one shape/size of aircraft and tweak them a little for your new design.