This is a plugin that allows for direct push or pull, site to site synchronization. An interesting feature is that it supports sites on localhost. Most migration plugins do not support localhost. There is both a free version and a premium version. The free version lets you synchronize the database from site to site. Note, this overwrites the database, it is not a merge.
The pro version is available from the WP Synchro website. It adds the ability to synchronize files as well. With the pro version you can also schedule syncs via the WP-CLI. The pro packages are available for 2, 5, 10, 30, or 100 sites for either monthly or annual subscriptions. The plugin has a good documentation section. Hat tip to Elvis Krstulović, who shared this plugin in the Dynamic WordPress Facebook group.