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.