Missing but needed SFTP ciphers

Seems like AES256-gcm and AES256@openssh are not supported. Please add support for those ciphers, Thanks!

I made a typo for the Open SSH I meant AES256-GCM@openssh

Indeed, WinSCP does not support the GCM ciphers.
WinSCP uses an SSH implementation from PuTTY project. Please consider asking for GCM support at their site.