Does the pedal move at all? As in will it go down far enough to establish that there is free play? If not, I would start by removing the clevis pin down on the bottom of the linkage rod where it connects to the arm that rotates the shaft through the clutch housing. In fact I would probably start there anyway. Then you can eliminate the pedal, pedal pivot bushings, and anything else external. Try to move the arm on the cross shaft by hand and see how far you can move it. That may be seized in the bores it rides in. If so, it won't move either way by hand. If it does move easily, but only goes so far (towards releasing the clutch) and stops, then you may have a throw out bearing carrier seized on whatever it rides on. That would mean a tractor split.
