title: X11 forwarding requested but DISPLAY not set
body: <p>I want to enable x11 forwarding on macOS connected to a Jetson Xavier nx. However, upon connecting:</p>
  <pre><code>sudo ssh -Xvvv id@host
  </code></pre>
  <p>The connection establishes successfully. But in the verbose logs, I'm getting the following:</p>
  <pre><code>debug3: send packet: type 50
  debug2: we sent a password packet, wait for reply
  debug3: receive packet: type 52
  debug1: Authentication succeeded (password).
  Authenticated to proto1 ([192.168.1.106]:22).
  debug1: channel 0: new [client-session]
  debug3: ssh_session2_open: channel_new: 0
  debug2: channel 0: send open
  debug3: send packet: type 90
  debug1: Requesting no-more-sessions@openssh.com
  debug3: send packet: type 80
  debug1: Entering interactive session.
  debug1: pledge: exec
  debug3: receive packet: type 80
  debug1: client_input_global_request: rtype hostkeys-00@openssh.com want_reply 0
  debug3: receive packet: type 91
  debug2: channel_input_open_confirmation: channel 0: callback start
  debug1: X11 forwarding requested but DISPLAY not set
  debug2: fd 4 setting TCP_NODELAY
  debug3: ssh_packet_set_tos: set IP_TOS 0x48
  debug2: client_session2_setup: id 0
  debug2: channel 0: request pty-req confirm 1
  debug3: send packet: type 98
  debug1: Sending environment.
  debug3: Ignored env TERM
  debug3: Ignored env SSH_AUTH_SOCK
  debug3: Ignored env PATH
  debug1: Sending env LANG = en_US.UTF-8
  debug2: channel 0: request env confirm 0
  debug3: send packet: type 98
  debug3: Ignored env HOME
  debug3: Ignored env MAIL
  debug3: Ignored env LOGNAME
  debug3: Ignored env USER
  debug3: Ignored env SHELL
  debug3: Ignored env SUDO_COMMAND
  debug3: Ignored env SUDO_USER
  debug3: Ignored env SUDO_UID
  debug3: Ignored env SUDO_GID
  debug3: Ignored env __CF_USER_TEXT_ENCODING
  debug2: channel 0: request shell confirm 1
  debug3: send packet: type 98
  debug2: channel_input_open_confirmation: channel 0: callback done
  debug2: channel 0: open confirm rwindow 0 rmax 32768
  debug3: receive packet: type 99
  debug2: channel_input_status_confirm: type 99 id 0
  debug2: PTY allocation request accepted on channel 0
  debug2: channel 0: rcvd adjust 2097152
  debug3: receive packet: type 99
  debug2: channel_input_status_confirm: type 99 id 0
  debug2: shell request accepted on channel 0
  
  </code></pre>
  <pre><code>X11 forwarding requested but DISPLAY not set
  </code></pre>
  <p>And in order for X11 forwarding to work, the DISPLAY variable must be set upon connection. Manually setting the DISPLAY like so:</p>
  <pre><code>export DISPLAY=http://localhost:22
  </code></pre>
  <p>doesn't work either. How to enable X11 forwarding?</p>