I imagine it’s a school by school thing…and perhaps he can apply to be in plays or musical groups.
I’m assuming engineering is his primary and theatre secondary but it could be reversed. My sons school has an engineering minor.
This article may be of interest…I just ran a Google search. I imagine the answer is yes.
My son is a MECHe with geography minor. Basically geography requires six classes. I’m sure he could minor in anything, perhaps including something performance related.
Good luck