Disable update of certain plugins.Put this file into /wp-content/mu-plugins/

disable-update-plugins.php

<?php
/**
 * Plugin Name: Disable updates plugins
 * Plugin URI: https://kagg.eu/en/
 * Description: Disable update of certain plugins.
 * Version: 1.0
 * Author: KAGG Design
 * Author URI: https://kagg.eu/en/
 * License: GPL2
 */

/**
 * @param mixed $value
 *
 * @return mixed
 */
function filter_update_plugins( $value ) {
	// Array of plugin slugs.
	$disable_update_plugins = array(
		'akismet',
	);

	if ( ! isset( $value->response ) ) {
		return $value;
	}

	foreach ( $value->response as $name => $plugin ) {
		foreach ( $disable_update_plugins as $disable_update_plugin ) {
			if ( stripos( $name, $disable_update_plugin ) !== false ) {
				unset( $value->response[ $name ] );
			}
		}
	}

	return $value;
}

add_filter( 'site_transient_update_plugins', 'filter_update_plugins' );