when I pour water over the cauldron, it doesn't fill up. the dispenser cannot fill the cauldron with water. but if this is the intended function, I don't understand why we can fill the anchor with a glowston (everything works on the mobile version). have a good day 🙂  (google translator soy :/ )
You have to right click the cauldron with the water bucket, not pour the water over it.
Dispenser not being able to interact with cauldrons is MC-9910.