In OpenBSD, all OpenSSH configurations are left to their defaults. That is reasonable, as OpenSSH is developed on OpenBSD.
X11 Forwarding is disabled by default for both the client and server.
- In the case of the server, sshd, it must be enabled via sshd_config.
- In the case of the client, ssh, it can be enabled via ssh_config, or via command line.
Using "-Y" has always worked for me, from an OpenBSD client, to any OpenSSH server with X11Forwarding enabled. I end up with a $DISPLAY variable, and the packets are tunnelled properly.
If 'ssh -Y <myserver>' does not work for you, then examine the sshd_config in use on <myserver>. If you can confirm X11 forwarding has been
explicitly enabled, with "X11Forwarding yes" then you must debug the configuration. Try 'ssh -v -v -v -Y <myserver>' and examine the debugging output.