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: https://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.
I want to mention this disclaimer, though: right now, at least in tech roles, it’s currently very difficult to actually land one of these jobs. Listings are getting hundreds of applicants per hour on some occasions. There’s a lot of competition because of recent return to office mandates and layoffs, and it might be awhile before that changes.