Wordpress generate_rewrite_rules is not working with multisite

Question

Below is a sample of a few redirects we are using in our theme. They all work correctly in a standard install of WordPress but do not work in a multisite installation. Is there a special code we have to run to enable these rewrites in multisite.

We have tried adding the multisite slug to the rewrite without success.

add_filter( 'generate_rewrite_rules', function( $wp_rewrite ){
        
    // Front End
    $uri = str_replace(home_url(),'',get_stylesheet_directory_uri());
    $uri = substr($uri,1); // remove trailing slash

    // Back End
    $adminuri = str_replace(home_url(),'',get_template_directory_uri());
    $adminuri = substr($adminuri,1); // remove trailing slash
    
    $feed_rules = array(
        // FavIcon forward
            $uri.'/favicon.ico' => 'index.php?favicon=$matches[1]',
        // Fonts for Dev Mode
            $uri.'/fonts/([^/]*)/([^/]*)/?$' => 'index.php?fontLoc=1&fontFace=$matches[1]&fontType=$matches[2]',
            $uri.'/fontawesome/([^/]*)/([^/]*)/?$' => 'index.php?fontLoc=2&fontFace=$matches[1]&fontType=$matches[2]',
            $adminuri.'/inc/css/fontawesome/([^/]*)/([^/]*)/?$' => 'index.php?fontLoc=2&fontFace=$matches[1]&fontType=$matches[2]',
        // Sitemap Redirect
            $uri.'/sitemap.xml' => $uri.'/wp-sitemap.xml'
    );
    $wp_rewrite->rules = $feed_rules + $wp_rewrite->rules;
    return $wp_rewrite->rules;
});