I am familiar with Max’s approach, and you are correct, Steve. He’s using encoders on all physical controls to drive servos/actuators/relays, which adds a lot of complexity but removes the requirement for physical linkage changes when transitioning from auto to manual (ride-on) control. The physical control sticks/levers will not have to move during auto operation. It’s a novel and interesting approach!
With this approach, it’s important to consider the Developer Code of Conduct, which states:
ArduPilot is NOT certified for use in applications where ArduPilot is effectively in control of human lives. Members of the development team must not knowingly assist in projects where ArduPilot will be in control of human lives. “In control of human lives” includes but isn’t limited to manned aircraft.
At face value, that indicates that the development team would shy away from involvement with or endorsement of such a vehicle. However, Randy made an excellent point of clarification regarding a possible wheelchair application in post 6, here:
Wheelchair guidance - ArduRover / Miscellaneous - ArduPilot Discourse
So as long as you’re careful to implement appropriate safety mechanisms, there shouldn’t be much resistance to discussing, implementing, and receiving help with a manual/automatic mower.