

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.
Graphene allows for fingerprint and second factor pin unlock, which is what I use. I mostly do that for cops, though, since in the US you can be legally compelled to unlock your phone with biometrics but not pin.
Wouldn’t stop someone from torturing you to unlock your device, but that’s what a duress pin is for ;) (they may kill you once your phone wipes but at least they wouldn’t have your data)