It is not officially supported to do this over SFTP… you’d need to stick to the MyCloud functions here.
But you could (at your own risk) edit the SSH daemon config to look like this
nano /etc/ssh/sshd_config
Port 22
Protocol 2
HostKey /etc/ssh/ssh_host_rsa_key
SyslogFacility AUTHPRIV
# you need to decide wether you want root/sshd here
AllowUsers admin userA userB
PermitRootLogin no
PubkeyAuthentication yes
PasswordAuthentication yes
ChallengeResponseAuthentication no
TCPKeepAlive yes
# remove deprecated stuff
#PubkeyAcceptedKeyTypes +ssh-dss
#HostKeyAlgorithms +ssh-dss
#Ciphers +blowfish-cbc
MaxAuthTries 5
Subsystem sftp /usr/bin/sftp-server
Then reload the ssh config
kill -HUP $(pidof sshd)
You’ll get kicked out of the session. Reconnect and you new config is active.
You can now login as admin, userA or userB.
