At Inpsyde we often use the Multisite Core feature to run multiple WordPress instances on one installation. We use the Multisite Core feature, for example, for customer projects and for MultilingualPress, our solution for multilingualism in WordPress. In conversations at WordCamps or other events, however, we often notice that Multisite is still an unknown function. The feature has been included in WordPress with version 3 since 2010. Already before, the function had a large user group as fork with the name WPMU (WordPress Multiuser). In addition, activating the multisite is relatively easy, see here. Therefore you can find in my contribution, which solutions the multi network WordPress Core feature offers.
This is already possible with the Multisite WordPress Core Feature
With multisites you can create complex networks of sites. For example, regional departments of companies where branch managers have administrative rights but cannot add additional designs or plugins. They can only choose from the pool of existing shared extensions and designs. Additionally, it is possible that a user with administrative rights has only editorial rights in another site.
In order to use it even better in larger companies, the WP Multi Network plugin makes it possible to manage additional networks on the same instance. Only one interface is added, because the WordPress core itself already has this function. With the internal separation of the networks, it is now, for example, possible for a regional manager to create a new site without having to go through a time-consuming setup process. There he can choose from all designs and plugins of the WordPress installation. These can also be activated automatically for all sites in the new network. This is helpful if certain plugins have to be activated regionally, for example the cookie hint in Europe.
For scaling (as it also uses wordpress.com), it is additionally possible not to run all database tables of the installation in the same database. By the extensions https://github.com/stuttter/ludicrousdb or https://wordpress.org/plugins/hyperdb/ a global separation of the sites is also possible. This would make it possible to operate the regional Japanese sites in Japan as well.
Further concepts can also be achieved with the multi network feature in order to make even more use of the flexibility of WordPress.