It all depends, how these categories are displayed in your theme.
If it’s done nicely and with proper use of WP template tags, then that list comes from get_the_category() function (all other functions are using this one).
And at the end of that function you can find
return apply_filters( 'get_the_categories', $categories, $id );
So it’s great news, because it means, that you can write your own filter and remove given category from the lists:
function prefix_remove_featured_category_from_post_categories_list( $categories, $id ) {
// do whatever you want with $categories list
// for example remove some category from the list
$categories_to_remove = array(
'cat-slug-a',
'cat-slug-b'
); // Array of categories slug to be remove. Put your slugs in here
foreach ( $categories as $index => $single_cat ) {
if ( in_array( $single_cat->slug, $categories_to_remove ) ) {
unset( $categories[ $index ] ); // Remove the category.
}
}
return $categories;
}
add_filter( 'get_the_categories', 'prefix_remove_featured_category_from_post_categories_list', 10, 2 );