XWiki
US alternative: ConfluenceEnterprise wiki and knowledge management platform with open-source foundations, extensibility, and cloud or self-hosted deployment.
Fully European
Overview
XWiki is a long-standing enterprise wiki and knowledge management product for organizations that want structured documentation, collaborative knowledge bases, and extensible internal information systems. It is relevant as a European alternative to products like Confluence and Notion in documentation-heavy environments. The product is backed by a French operating company, has an explicit open-source foundation, and offers productized cloud and service layers for real production use.