Exclude images without specific class/attribute from WP Rocket lazyload [WordPress]

exclude_hard_images_from_ll_wprocket.php

//rocket_buffer in theory should work no matter if gallery/slider is in the_content or not, inserted via js etc
//they don't have class and it's not possibleto assignit specifically to img elements -- here is what we can do
//we need to know: smallest parent element that contains them all
//checked -- it doesn't impact those exclusions added via ui

add_filter('rocket_buffer', 'sz_exclude_images_without_class_from_ll');
function sz_exclude_images_without_class_from_ll($buffer) {
    $document = new DOMDocument();
    libxml_use_internal_errors(true);
    $document->loadHTML($buffer);
    $xpath = new DOMXpath($document);
    $expression = './/figure[contains(concat(" ", normalize-space(@class), " "), " wp-block-gallery ")]';
    foreach ($xpath->evaluate($expression) as $parentelement) {
        //get all images inside the parent node (img can be changed to picture tag)
        $imgs = $parentelement->getElementsByTagName('img');
        if ($imgs->length > 0) { //if there are images found
            $i = 0;
            foreach ($imgs as $img) if ($i < 1) { //ajust limit number here (for slider or gallery for example)
                $image_src = $img->getAttribute('src');    //get image src
                $image_srcs[] = $image_src; //all images' src
                $i += 1; //counter
            }
        }
        break; //take the first parent element only if there are few
    }

    //Add what our list to the WPR LL exclusion!
    add_filter('rocket_lazyload_excluded_attributes', function ($attributes = []) use ($image_srcs) {
        $attributes = array_merge($attributes, $image_srcs);
        return $attributes;
    });

    return $buffer; //return buffer content unchanged
}

Doesn’t work — no-lazy added after lazyload script initialized — sequence is not right

the first version via JS didn't work (but I guess it might with some tweaking with passing variables back via AJAX.
But the updated one via WP Rocket PHP filters direct -- works :)