WordPress fallback post instead of 404

wordpress-404-fallback-post.php

<?php
add_action(
	'wp',
	function () {
		global $wp_query;

		if ( ! $wp_query->is_main_query() || ! $wp_query->is_404() ) {
			return;
		}

		$wp_query = new WP_Query(
			[
				'post_type' => 'page',
				'p'         => 2,
			]
		);

		remove_action( 'template_redirect', 'redirect_canonical' );
	}
);