WordPress: Disable blocks for all users on certain post types. See details https://silvanhagen.com/writing/disable-wordpress-blocks-for-all-users/

functions.php

<?php

add_filter( 'allowed_block_types_all', function( $allowed_blocks, $editor_context ) {
    
    if ( in_array( $editor_context->post?->post_type, ['post', 'page'] ) ) {

        $blocks = array_diff( 
            array_keys( WP_Block_Type_Registry::get_instance()->get_all_registered() ),
            [
                'core/image', 
                'core/headline', 
                'core/buttons', 
                'core/button', 
                'core/column', 
                'core/columns', 
                'core/more',
                'core/nextpage',
                'core/text-columns',
                'core/comment-template',
                'core/cover',
                'core/media-text',
                'core/freeform',
                'core/code',
                'core/preformatted',
                'core/verse',
                'core/query',
                'core/archives',
                'core/calendar',
                'core/categories',
                'core/latest-comments',
                'core/latest-posts',
                'core/search',
                'core/tag-cloud',
                'core/rss',
            ]
        );
        return array_values( $blocks );

    }

    return $allowed_blocks;

}, 100, 2 );