https://en.wikipedia.org/wiki/Thing-in-itself
I don't think it follows that either the universe or our minds are computational. For one, we don't have a satisfactory definition of "mind", so that question has to remain open until we do.
And the universe could be "computational" in a completely unfamiliar way. It might even be humanly unimaginable.
As a wild speculation, consider the extreme case: the universe actually functions as an indivisible whole.
We use math to make predictions about repeating causal patterns, and invariably they work in a time- and precision-limited way. If the universe was a true thing-in-itself on its own terms, it could be "computational", but our models would always be incomplete and imperfect.
We would never be able to understand it fully, because we would never be able to build a complete and accurate representation of its computational mechanisms.