How to prevent WordPress scaling large images down

Question

I've tried the following code in the active child theme's functions.php to prevent the large digital print JPGs from being scaled down, but it didn't succeed:

function remove_all_image_sizes() {
    foreach ( get_intermediate_image_sizes() as $size ) {
            remove_image_size( $size );
    }
}
 
add_action('init', 'remove_all_image_sizes');

Can you help me 'turn off' WordPress scaling down large images please?

Help appreciated.