Besides OpenSSH/cygwin the only other free SSH servers for a Windows platform that I have tried were
OpenSSH for Windows and
freeSSHd. I tried an early version of freeSSHd but had issues with getting private\public key pairs to work right.
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freesshd.com/index.phpI don't know if its actively maintained, etc or not. As you know all maintenance of OpenSSH for Windows stopped over two (2) years ago making that a non-starter as far as I am concerned...
Once I found copSSH I have stuck with that particularly since it is actively maintained and updated as OpenSSH/OpenSSH/cygwin are updated...
Good luck...