SFTP server with storage encryption

I’m looking for an unusual solution that uses SFTP server for data transfer but said SFTP server also should act an encryption proxy i.e. all the data it stores on the server side should be encrypted. Although I could use host (OS-wide) encryption it is not gonna be effective during runtime if the hoster I use decided to peek at it or will be forced by 3rd party or crappy government.

I did some googling but the only thing I found was: https://github.com/libfuse/sshfs Problem is I dont want no custom clients, I want to hide ANY implementation from the client, it should be just your basic SFTP you can use anywhere, even on your microwave, let alone phone or notebook.

This variant: https://serverfault.com/questions/887167/sftp-with-data-encryption-at-rest seems useable but again, at runtime it only protects against other normal users (which I dont have).