Most ferns are not nibbled by deer. Some will do okay, once well-established) in dryish locations. Wood ferns might be a good choice. Fedco sells them, but calls them leatherwood firms. They are also known as Marginal Shield ferns. Mine have done pretty well in dry shade.

Leatherwood Fern - Fedco Trees

Landscape Plants Rated by Deer Resistance (Rutgers NJAES)

You could plant large ornamental grasses --native Panicums would work--on the sunny side (south side) of the trees. Deer never eat them.

Deer will not eat Rosemary and varieties can grow fairly big....big enough to hide the box. Plant far enough out in full sun.

You could raise the electric box on legs the same height:)

Plant something in front. And Yes! to consulting the Rutgers’ Deer Resistant plants list! It’s the most reliable that I’ve found.