Hello,
I would highly recomend you to take a look at this amazing topic!
It is very informative in terms of Canbus steer-ready tractors!
New CNH tractors use a standard Danfoss autosteer valve which is no problem to control via CAN.
The CANBUS steering expert @CommonRail and others did some amazing work and figured out how all that is working.
The most recent “state of the art” solution would be the Teensy Canbus PCB he designed. WIth that you can connect three CAN-busses at once to the Teensy and have basicaly full control of your tractor. Steering it over the steering bus, use a joystick button to engage steering or let AOG push the headland management button for you.
It even can read the actual hitch height from ISOBUS and use it for the AOG workswitch.
Here is the Github Link for this PCB: GitHub - MechanicTony/AOG_CAN_Teensy4.1: AgOpenGPS using Teensy4.1 and CANBUS AutoSteer Ready Tractors
The AIO 4.1 does work with a different Code for steering via CAN but then you don’t have the option to use the other CAN networks of your tractor.
I hope I could help you. I’m currently upgrading my steer ready tractor to this PCB from previously just steering it with an Arduino Uno with canbus shield. Did also work flawlessly for two years! 
At any questions feel free to ask.