Timber – Twig post.content returns null can’t create ACF Gutenberg blocks

You will need to add the current page object to the timber context using timber_context filter.
Something like this

add_filter('timber_context', 'bt_timber_add_to_context');
function bt_timber_add_to_context ($context) {
    // add current page content
    $context['page'] = Timber::get_post();

    return $context;
}

That’s how I added it in my custom timber theme.
Now when you want to get the page content you can do this

{{ page.content }}

This is availalbe only if you use Timber::context() in your render/compile methods.
Basically if you use Timber::context(), one of the object properties will be page