GUI Applications with X11 Forwarding
If things are not opening, try running
echo $DISPLAY on the server. If nothing comes up, a possible fix on macOS is to install XQuartz, run
launchctl load -w /Library/LaunchAgents/org.macosforge.xquartz.startx.plist on the Mac, then restart the computer. For debugging, try using
ssh -v -X <e.g. WS2>.
To open the Seafile GUI remotely (annoyingly, the GUI allows adjusting some settings that the CLI does not have), run