Ask HN: What document-sharing solution you can recommend?

Hey HN guys - What document-sharing solution you can recommend in consideration of these requirements? > Requestor is NGO - school for autistic kids from middle europe country. Ca 40 employees > Shared data : attendance, internal and external projects, internal school/students data > Users are not technical so simple and user-friendly GUI is needed. > Google, Microsoft, Amazon solutions are not applicable. > Price is critical (open source license / self-hosted solution would be great) > Usage and features - interal use for document sharing, comment/post notes is required, version control or some kind of history log, possible mail notification Do you have any knowledge about suitable products/projects? In case of further interest for deeper discussion in private, you can reach me out via my profile. Thank you indeed.