The closest thing I can think of is Nextcloud [1]. You can host it yourself or get them to host it for you. It encrypts files at rest. That is transparent to

The closest thing I can think of is Nextcloud [1]. You can host it yourself or get them to host it for you. It encrypts files at rest. That is transparent to the user. You or someone have to be technically savvy to set it up, but the users should be ok. File transfers, messaging, etc... all encrypted. [1] - https://nextcloud.com/ https://nextcloud.com/