How do I use a font package but keep math font unchanged?

Question

I am using two font packages: fourier (which is in fact Utopia) for overall text and chivo for sans-serif.

However, I don't like the changes these packages make to math font. I tried to revert math back to Computer Modern with the following commands:

% Revert mathcal back to `cms` -- it works
\DeclareMathAlphabet{\mathcal}{OMS}{cmsy}{m}{n}

% Attempt to revert all math back to `cms`: does not work
\DeclareMathAlphabet{\mathsf}{OMS}{cmsy}{m}{n}

I also tried replacing \mathsf with \mathnormal and \mathroman to no avail.

Here's my minimal reproducible example:

\documentclass[11pt]{report}
\usepackage[T1]{fontenc}

\usepackage{fourier}
\usepackage[scale=0.9]{Chivo}

% Fix \mathcal but no success changing overall math font
\DeclareMathAlphabet{\mathcal}{OMS}{cmsy}{m}{n}
\DeclareMathAlphabet{\mathsf}{OMS}{cmsy}{m}{n}

\begin{document}
Math calligraphy looks ok, but arrows are ugly: 
$$P \rightarrow \mathcal{O}(n^2) \wedge \leftrightarrow 8$$
\end{document}

Answer 1

It is better to avoid that fourier change the math, so don't load the package but change only the font family:

\documentclass{article}
\renewcommand{\rmdefault}{futs}
\RequirePackage[T1]{fontenc}
\usepackage[scale=0.9]{Chivo}


\begin{document}

abc \sffamily abc

\end{document}