I will start by saying that I personally do believe that the brain
is a computer, with the minnd simply being software.
However, given our current level of understanding of how the mind works, we can't say for sure that certain thoughts are algorithmic. For example, we don't know an algorithm by which new systems of axioms can be created, nor even a general algorithm for proving a theorem in a given system of axioms, beyond brute force searching. Given that human minds do these things relatively often, it's unlikely they are arriving at it by brute force search in the enormous domain of mathematical statements.
So, we can't say we've ruled out the possibility that the mind is using some unknown non-computational process for finding novel theorem proofs. Note that proof checking is algorithmic, only proof discovery is potentially not.
Now, to me extrapolating this to a non-computational theory of mind smells a lot like a God-of-the-gaps argument, so I don't buy it. But it is worth remembering the limits of what is actually proven to be computable.
I've taken this example somewhat directly from Turing's paper on computation - there, he bases the model of the Turing machine specifically on a mathematician doing rote mechanical calculation with a pen and paper (the machine state is their brain state, the tape is the notebook, the writing head is the pen, and the reading head is their eyes). However, non-rote calculations are arguably left out of the paper's claims (or at least most of them).
Much more famous arguments about non-computational theories of mind are, to me, much less convincing. The most famous is probably The Chinese Room, where the idea is that a man locked in a room receives a question on paper written in Chinese characters, and follows lookup tables and English instructions to return another paper written with Chinese characters, but can't really be said to understand Mandarin even if he is always returning the right answer for the question asked (or so the author claims). Another such famous argument is Mary's Room, where Mary is also locked in a room where nothing has the color red, but where she gets to rid everything that can be known about the physics and biology of the color red and its perception in the human brain (much more knowledge than we have today), but where she is assumed to still have a new experience once she leaves the room and actually sees red for the first time directly.