WPMU DEV provides managed WordPress hosting, WordPress plugins and tools for managing multiple websites. For hosting, customers choose the region in which their site is stored; according to the documentation, WPMU DEV partners with Vultr and maintains hosting regions on several continents. The service is delivered as a hosted platform, complemented by plugins that run on a customer's own WordPress installation.
According to its own about page, WPMU DEV is headquartered in Melbourne, Australia. The privacy policy, however, is published by Incsub, LLC, a US entity, and the company states that it is listed on the EU-US Data Privacy Framework and registered with the UK's ICO. A data processing agreement is available on request. For European organisations the key point is that an EU hosting region can be chosen, but the vendor is established outside the EU and operates through a US entity; check the data processing agreement and sub-processors before use.