Hydraulic steering to use with AgOpenGPS? If so, yes, it certainly is possible. @Baraki sells a valve block made for this purpose. See the very long thread at Hydraulic valve assemblies for Every tractor, for every type of hydraulic system
Or if you mean use Deere Autotrac steering with a hydraulic block that is probably possible, but you’d need a John Deere valve and also a SSU module, so quite expensive.