There is a tool for Brep topology that gives you, for each edge, the indices of the adjacent faces. You can use this to work out the angle between the Z axis of the face planes.
Does this give you the dihedral angle? I always get paranoid that I’ve calculated the wrong angle…
FACE_ANGLES.gh (18.6 KB)
(I don’t know if the Brep Topology component is standard GH or not.)