WP Render Block Filter

filter_render_block.php

/**
 * @param $block_content
 * @param $block
 *
 * @return string
Surrounds block with html.
 * Some blocks are too naked to work nicely like ul
 */
function surround_block( $block_content, $block ) {
	if ( empty( trim( $block_content ) ) ) {
		return $block_content;
	}

	if($block['blockName'] == 'core/list'){
		return sprintf(
			'<div class="block-%1$s">%2$s</div>',
			sanitize_title( $block['blockName'] ),
			$block_content
		);
	}
	return $block_content;


}
add_filter( 'render_block', 'surround_block', 10, 2 );