> ssh -vv -X user@host
>
> but I haven't seen anything suspicious. xauth is installed in the normal
> location and seems to run correctly (although I'm really not familiar
> with it). In my sshd_config file, the relevant options are set as:
>
> X11Forwarding yes
> X11DisplayOffset 10
> #X11UseLocalHost no
> #UseLogin yes

I enabled the following in my sshd_config

X11Forwarding yes
X11DisplayOffset 10
X11UseLocalhost yes

and the following in my ssh_config

ForwardX11 yes


then when I ssh to the remote host with the -X option,
and echo $DISPLAY it's set.