My ‘96 Kubota has two *start-safety switches….the Range Lever MUST be in ”Neutral” for the starter to operate. That switch is not obvious…. it is under the deck near the Range Lever mechanism.
UN-plug the leads at that switch… They are simple male/female connectors. Unplugging them will disable the starter.
It has another safety-switch… the PTO lever must be Disengaged also. I suppose one could disable that as well….
One could “lock-wire” the fuel shut-off/shut-down also.