Workaround for Simple Share Buttons and front end caching

disable-wp-is-mobile.php

<?php
/**
 * The Simple Share Buttons uses wp_is_mobile() to decide how to render front end
 * pages, which is incompatible with frontend caching. So filter the check
 * to always return the "mobile version" (unless we are in the admin backend).
 * 
 * Bbeware! It overrides _all_ frontend calls, not just SSBA ones).
 *  
 * Save this as a mu-plugin ( wp-content/mu-plugins/disable-wp-is-mobile.php )
 * or paste it into your functions.php file
 * 
 * @see https://wordpress.org/support/topic/disable-wp_is_mobile-checks/
 * @see https://developer.wordpress.org/reference/functions/wp_is_mobile/
 * 
 */
add_filter( 'wp_is_mobile', function($is_mobile){
    if (!is_admin()) {
        return true;
    }
    return $is_mobile;
});