Would not shift - manual

That could be the clutch, transmission, transfer case or rear differential. Lets try some tests to see if we can narrow it down. First would be to check and be sure the transfer case didn't get into neutral, Shift it to 4 high and see if the truck moves. This would narrow down the items as putting it into 4 high, will engage the front end, if it starts moving there, but not in 2wd, then it's likely the rear end. If it still doesn't move it isn't the rear or front and is now the transmission or transfer case. Next try putting it in the other gears and see if the truck will move when pushed.
Testing beyond that will require getting under the truck and removing the inspection cover from the front of the transmission and looking at the clutch assembly to see if something there failed, like the throw out bearing sticking or the pressure plate failing. To check the rest requires that the transmission and transfer case be removed to see if there is internal damage like an input shaft or similar that has failed.

One of the low priced inspection cameras that work with a phone or tablet or if the parts store has a rental version would let you look up in there easier and see if the input shaft rocks when the truck moves while in gear. You should be able to se the edge of the clutch disc as well.