What do you call a person that goes for functionality, yet not for the beauty of set things?

I would call that person a Minimalist.

belonging or relating to a style in art, design, and theatre that uses the smallest range of materials and colours possible, and only very simple shapes or forms:

-Cambridge Dictionary on-line

They don't do anything more than necessary. However, I feel that there's a better word for it.

EDIT: I think the better term for it I had on my tongue is a Pragmatic person.

pragmatic : relating to matters of fact or practical affairs often to the exclusion of intellectual or artistic matters : practical as opposed to idealistic

-Merriam Webster on-line

Philistine

From Collins Dictionary:

If you call someone a philistine, you mean that they do not care about or understand good art, music, or literature, and do not think that they are important.

Collins

Or,

a person regarded as smugly narrow and conventional in views and tastes, lacking in and indifferent to cultural and aesthetic values

Ibid

How about prosaic?

From Cambridge:

without interest, imagination, and excitement:

If only she'd been called Camilla or Flavia instead of the prosaic Jane.

He asked if I'd got my black eye in a fight - I told him the prosaic truth that I'd banged my head on a door.

Utilitarian

adjective

1. designed to be useful or practical rather than attractive.
   "a utilitarian building"

[Lexico]

You could describe this individual as a no-frills type of person. This indicates that they prefer things that are stripped down to their minimal functional elements, and do not have any "extra" features that don't directly contribute to functionality. These frills could be things like art or decoration, but could encompass anything not directly related to the main purpose, like getting a bag of peanuts on an airplane. No-frills implies functionality first, without much consideration for beauty/comfort/enjoyability or any other secondary goal.

Another fitting word would be to simply describe the person as being practical. This again indicates that the person is primarily concerned with functionality above other considerations. It doesn't necessarily suggest an explicit avoidance of "extra" features like no-frills does, but it does place the highest value on functionality.