Collaboration software combines chat, video meetings, shared files and co-editing of documents in one workspace. Organisations use it for daily communication, for working with external partners, and increasingly as the place where decisions and project history are recorded. Well-known reference points are Microsoft 365 with Teams, Google Workspace and Slack.
The sovereignty issue is accumulated context rather than a single data set. Chat history, recordings, file versions and sharing logs together describe how your organisation works, and the metadata is often as revealing as the content. A provider under foreign jurisdiction can be compelled to disclose it, regardless of which data centre holds it. Lock-in is the second risk: when channels, documents and integrations rely on proprietary formats, leaving becomes a project in itself.
When assessing a European option, look at open document formats and open standards for messaging and calling, guest access without an account on a foreign platform, controls over retention and recording, and whether a self-hosted or dedicated deployment is offered. Ask for a documented export of messages, files and permissions.