In the past, when I’ve used SFTP, I just use the openssh docker container with a mount of my filesystem (since SFTP uses SSH). Particularly this image: hub.docker.com/r/linuxserver/openssh-server

I can’t speak to sftpgo as I haven’t used it, but from looking it up it seems that some people like it, although it’s a pain to set up. If you want something simple I’d still just go with openssh.