Showing splash webkit window to have a view on what's happening

I'm trying to show the browser window of splash in order to have look at what's happening under the hood and see if there is some captcha or any other strange result ...

I've tried running the container in this way:

 docker run --name "splash-debug" -e DISPLAY=$DISPLAY \
             -v /tmp/.X11-unix:/tmp/.X11-unix \
             -v $XAUTHORITY:$XAUTHORITY \
             -e XAUTHORITY=$XAUTHORITY \
             -p 8050:8050 \
             -it scrapinghub/splash --disable-xvfb

 but I still can't see any browser window... Am I doing something wrong here ?