Allow excerpt for pages in Gutenberg?

I’d like to utilize excerpt field on pages. How do I enable it?

Currently excerpt block only shows on posts in sidebar. But on pages it’s missing.

It’s nothing new with the block editor, it’s the same age-old way by putting the following code into your theme’s functions.php:

add_action( 'init', 'wpse325327_add_excerpts_to_pages' );
function wpse325327_add_excerpts_to_pages() {
    add_post_type_support( 'page', 'excerpt' );
}

Here’s my screenshot in a fresh WordPress 5.0.3 install: