Activate Yoast SEO plugin's meta box on Event Espresso CPT editor routes.

yoast_seo_boxes.php

<?php
//* Please do NOT include the opening php tag, except of course if you're starting with a blank file

add_action('plugins_loaded', 'my_ee_yoast_seo_box');

function my_ee_yoast_seo_box() {
    if (
        ! empty($_GET['page']) 
        && 
        in_array(
            $_GET['page'],
            array(
                'espresso_events',
                'espresso_venues',
                'espresso_people'
            )
        )
    ) {
        add_filter(
            'wpseo_always_register_metaboxes_on_admin',
            '__return_true'
        );
    }
}