qemux86-64:~# cat /run/platform/display/compositor.log 
Date: 2020-07-29 UTC
[19:35:20.788] Using config file '/etc/xdg/weston/weston.ini'.
[19:35:20.789] Output repaint window is 7 ms maximum.
[19:35:20.790] Loading module '/usr/lib/libweston-8/drm-backend.so'
[19:35:20.798] initializing drm backend
[19:35:20.801] logind: not running in a systemd session
[19:35:20.801] logind: cannot setup systemd-logind helper (-61), using legacy fallback
[19:35:20.808] no drm device found
[19:35:20.808] fatal: failed to create compositor backend.
Date: 2020-07-29 UTC
[19:35:21.333] Using config file '/etc/xdg/weston/weston.ini'.
[19:35:21.343] Output repaint window is 7 ms maximum.
[19:35:21.343] Loading module '/usr/lib/libweston-8/drm-backend.so'
[19:35:21.345] initializing drm backend
[19:35:21.356] logind: not running in a systemd session
[19:35:21.356] logind: cannot setup systemd-logind helper (-61), using legacy fallback
[19:35:21.356] /dev/tty7 is already in graphics mode, is another display server running?
[19:35:21.361] fatal: drm backend should be run using weston-launch binary, or your system should provide the logind D-Bus API.
[19:35:21.361] fatal: failed to create compositor backend.
Date: 2020-07-29 UTC
[19:35:22.307] Using config file '/etc/xdg/weston/weston.ini'.
[19:35:22.307] Output repaint window is 7 ms maximum.
[19:35:22.307] Loading module '/usr/lib/libweston-8/drm-backend.so'
[19:35:22.313] initializing drm backend
[19:35:22.314] logind: not running in a systemd session
[19:35:22.314] logind: cannot setup systemd-logind helper (-61), using legacy fallback
[19:35:22.314] /dev/tty7 is already in graphics mode, is another display server running?
[19:35:22.314] fatal: drm backend should be run using weston-launch binary, or your system should provide the logind D-Bus API.
[19:35:22.314] fatal: failed to create compositor backend.