Can Fire Foam (a 3M product) can be used to cover a hole from a missing knockout in an electrical panel?
This is the proper method of closing a panel hole .
I would not even consider using foam . No foam is not the proper way to close a hole .
As Roy stated no because the foam is not substantially equivalent to the KO. Here’s the NEC reference.
Have never seen a mouse chew through a metal snap cap, but they seem to love all foam products. Unless the mnf rates their foam for electrical panels I would call it out.