Remote kiosk debugging

Start the X server only from its intended local console session. After that session is running, an SSH session for the same user can attach an application to the existing display by setting the appropriate display and user runtime environment.

export DISPLAY=:0
export XAUTHORITY=/home/app/.Xauthority
export XDG_RUNTIME_DIR=/run/user/$(id -u app)

This is a debugging workflow, not a mechanism for starting an X server over SSH. Check the target application’s display and authentication expectations before attaching it. The complete local-console STARTX policy belongs on the STARTX runner page; do not replace it with startx from an SSH session.