Question 1: Does the shifter move/transmission shift when the car is off?
If yes -
Possible problems in decreasing order by easiest to check:
1. Bent or broken clutch fork
2. Failed Slave Cylinder
Check those two together by watching for full stroke/movement while someone pushes the clutch
3. Broken pedal assembly - just inspect; search for TRE inspection method
4. Failed Master Cylinder - Bleed it at the slave to see if it is building pressure for starters
5. Destroyed clutch disk - springs came loose, contact surfaces came off or crumbled and got things stuck - you might be able to see through the clutch fork hole or flywheel inspection plate but pull trans to know for sure
That's where I'd start based on various fun times I've had.
Oh - if the answer to question 1 was "No" then start with shift cables/linkages see if you can move the shift forks and sliders manually at the trans. If not...pull it out. It probably broken.