Make the public key directory – mkdir /home/$User/.ssh

Make the key file to hold the key touch /home/$User/.ssh/authorized_keys

Give the user ownership of their key folder – chown $User:$User /home/$User/.ssh && chown $User:$User /home/$User/.ssh/authorized_keys

Modify permissions on ssh folder – chmod 0700 /home/$User/.ssh

Possibly modify the key file permissions – chmod 640 /home/$User/.ssh/authorized_keys <— Not 100% if this needs to be done try without it first and if it wont work add it in

Add the public key – /home/$User/.ssh/authorized_keys

Restart ssh – systemctl restart sshd

^ This. I added SSH key in and server refuses everytime and requires password

‘https://github.com/drakkan/sftpgo’

it has chroot support builtin, virtual quota, atomic uploads, bandwidth throttling and many other features.

It can execute configurable custom commands and/or send HTTP notifications on upload, download, delete or rename.

It is written in Go, so no runtime dependencies, and it works on Windows too

%h means users will directly land into its home directory when they do sftp command.
internal-sftp is a configuration keyword that tells sshd to use SFTP server code built-into sshd.
You need to set the required permissions on User’s home directory