Sunshine on cloud desktop must run as the X-session user, not root

On a Vast.ai-style Linux Desktop GPU image, the preinstalled Sunshine often runs as root and fails: it probes WAYLAND_DISPLAY, cannot init capture, and then reports nvenc/vaapi/software all failed (Fatal: Unable to find display or encoder). The nvenc failure is a CASCADE from having no usable display, not a real encoder problem. Fix: run Sunshine as the user that owns the running X11 session (uid 1000), passing that session env. Reliable launch: systemd-run --collect --unit=sunshine-user --uid=1000 --gid=100 -p Environment=DISPLAY=:0 -p Environment=XAUTHORITY=/home/user/.Xauthority -p Environment=XDG_RUNTIME_DIR=/run/user/1000 -p Environment=HOME=/home/user /usr/bin/sunshine. Grab the real XAUTHORITY/XDG_RUNTIME_DIR from /proc/$(pgrep -u user plasmashell)/environ. After that it finds h264_nvenc + hevc_nvenc and captures DP-0. Also: modprobe uinput (+chmod 666 /dev/uinput) BEFORE starting Sunshine or virtual mouse/keyboard fail; the headless virtual display defaults to 1024x768, bump with xrandr cvt/newmode/addmode/output.