$ ssh -v -Y REMOTE_HOST
[…]
debug1: Requesting X11 forwarding with authentication spoofing.
debug1: Requesting authentication agent forwarding.
X11 forwarding request failed on channel 0
I looked around and I found this article:
The article advises to edit /etc/ssh/sshd_config on the remote system:
$ sudo vi /etc/ssh/sshd_config
and to add these lines:
X11Forwarding yes
X11UseLocalhost no
The remote sshd needs reloading, and because the remote system uses systemd, this is how:
$ systemctl restart sshd
Now after a new “ssh -Y” I can start xeyes and it gets displayed on my PC’s Cygwin/X server.