[Plugin: Sort Query Posts] How to randomize ALL posts within a category

but rather shuffles the order of the posts that appear on each archive page.

Yes, that’s the intended behavior.

Is there a way to get it to randomize ALL posts within a category so that different posts can appear on the first archive page?

Not with this plugin.

Regards,

Túbal

Try Below code..

1. Select the post from category:
$args = array(‘cat’ => $category_id,’post_status’ =>’publish’,’posts_per_page’=>-1,’orderby’ => ‘post_date’,’order’=>’DESC’);
$random_posts_arr = query_posts($args);

2. shuffle or randomize the post array…
$post_arr = shuffle($random_posts_arr);

3. Then traverse the post array ($post_arr) to show the post data (title, link, image, date)