Trick WP Pagenavi with a fake WP Query in order to use custom contents which are not WP ones.

fake-wp-pagenavi.php

<?php
/**
 * Trick WP Pagenavi with a fake WP Query ¯\_(ツ)_/¯
 *
 * We use this method to earn time by using wp_pagenavi() method :
 * - no need to reinvent the wheel, the complicated algo is already done
 * - it automatically generates the html which is already stylised
 * - use wp_pagenavi options from dashboard
 * - whereas using custom contents which are not WP ones
 *
 * @url : https://fr.wordpress.org/plugins/wp-pagenavi/
 *
 * @author Maxime CULEA
 */

// Your customization goes here
$posts_per_page = 12;
$posts_found    = 45;

// Set basics args in order to pagenavi to work
$fake_query = new WP_Query();
$fake_query->set( 'posts_per_page', $posts_per_page );
$fake_query->set( 'paged', (int) empty( get_query_var( 'paged' ) ) ? 1 : get_query_var( 'paged' ) );
$fake_query->max_num_pages = (int) ceil( $posts_found / $posts_per_page );

wp_pagenavi( [ 'query' => $fake_query ] );