How do I prove that the Pi and T models of a BJT are equivalent?
Since these are linear circuits, they must be modelable with Thevenin models.
Or Norton. Or any method combining these.

I suggest you short the input, then drive the output with voltage sources and also a current source, in 2 phases. Show the equivalence.

Then open the input, and drive the output with voltage souces and then a current source, in 2 phases. Show the equivalence.

OR you may prefer to short the output, and drive the input with the 2 phases.
Then open the output, and drive with the 2 phases.