X11Forwarding yes ssh -X vs. ssh -Y

[Christoph Kukulies]

When logging into my FreeBSD12.1  system using 

ssh -Y user at mybox

and do echo $DISPLAY I get localhost:10.0 and can do X11Forwarding (which I enable in sshd_config)
Doing


ssh -X user at mybox

doesn’t work. DISPLAY variable is not being set.

Any clues? 

—
Christoph