Home Assistant is an open source home automation platform started in 2013 by the Dutch developer Paulus Schoutsen. It runs locally on hardware you own, from Home Assistant Green and Yellow to a Raspberry Pi or any spare server, and it integrates thousands of devices and services from different manufacturers.
Home Assistant is listed as open source and self-hosted rather than by company location, so the project itself is not necessarily European. Everything runs on your own hardware with no cloud requirement, and the commercial backer Nabu Casa sells optional remote access. Run on European hardware it is a European alternative to the American cloud platforms, and it suits people who want automation that keeps working when the internet does not.