How do I change the Multisite URL?

There are 5 values need to change.
From database.

wp_options: options named “siteurl” and “home”

wp_site

wp_sitemeta: the option named “siteurl”

wp_blogs: any entries in the “domains” column that have the old domain name

wp_#_options: Each sub-site will have sets of tables that correspond to the blog_id in the wp_blogs table. You need to go to the wp_#_options table, where # corresponds to the blog_id, and update the “siteurl” and “home” settings in that table.

Note: In most cases, you may/will need to update an entry in your WP-Config.php file. The code I would recommend taking a look at is the code snippet here:

define('WP_ALLOW_MULTISITE', true);
define( 'MULTISITE', true );
define( 'SUBDOMAIN_INSTALL', true );
$base="https://wordpress.stackexchange.com/";
define( 'DOMAIN_CURRENT_SITE', 'mysite.com' );
define( 'PATH_CURRENT_SITE', "https://wordpress.stackexchange.com/" );
define( 'SITE_ID_CURRENT_SITE', 1 );
define( 'BLOG_ID_CURRENT_SITE', 1 );