Comment by gsf_emergency_2

I don't exactly know what you mean but from your hint I found the uh, clarifying bedtime story:

https://arxiv.org/abs/2302.09687

(On functions of 3rd-order "tensors")

((Whereas matrix-functions are of 2nd-order "tensors"))

Playground: https://gitlab.com/katlund/t-frechet

(MATLAB)