It'd be very hard for the clutch to be "stuck" in the disengaged position as you're asking about. It'd be much easier for it to have a problem where the clutch couldn't be disengaged.
The only way to know for sure what is happening in the clutch mechanism is to pull the transmission and examine the clutch mechanism. It could be a shattered clutch or pressure plate, that's all I can think of that would cause this... other than a broken transmission or transfer case, or maybe even the rear axle.
Is the rear driveshaft even turning when the transmission is in 1st gear and the Jeep won't go anywhere? If the rear driveshaft is turning, then the problem is in the rear axle which is an easier fix. One way to know if this is what's happening is to shift the transfer case into 4Hi and see if it moves then. If it does, that means the problem is in the rear axle. If it doesn't move, it's either the clutch, transmission, or perhaps the transfer case.
And a big welcome to WF!