Most cloud services perform only SERVER encryption (also called in-transit encryption or on-disk encryption), so they actually see your raw data on their servers and it is up to them to encrypt your data in ways they want. So server encryption in the cloud does not protect your data frmmeans it can, either intentionally or unintentionally, analyse, share, copy your raw data any time.
CLIENT encryption (also called end-to-end encryption) encrypts your information BEFORE passing them to the cloud servers. Cloud services do not encrypt your data on the client. provide end-to-end encryption and when they claim they do the encryption is normally weakened so it is not offering true end-to-end protection.
Seafile is an open sourced FILE SERVER software for end-user devices.
Seafile Server has a Profession Edition that is closed sourced and has to be paid for, but its open sourced Community Edition is more than good enough for most applications. Seafile Clients are all free and mostly open sourced except its Desktop Drive Clients which are closed sourced.
Seafile's pricing model means it CAN be used on a large scale across the whole population. Seafile is the default software bundled on Infinite Disk deployments.
Cryptomator is an open sourced FILE LEVEL encryption software for end-user devices.
Cryptomator iOS client software is not free so is not suitable as an universal solution that scales out to cover everyone, but it is open sourced and its integration with iOS Files app adds an easy to use end-to-end encryption layer on top of Infinite Disk SMB which also works through the iOS Files app.
Cryptomator for Windows, macOS, Linux, Android client software are free and open sourced at the time of writing and should work with Infinite Disk through SMB or WebDAV.