You could use the xbmc-send command with the PlayMedia() action.
Example with URL (for your usecase you could place a file on the sdcard and give the full path and name instead of an URL):
Codekodi-send --action 'PlayMedia("http://www.sample-videos.com/video/mp4/720/big_buck_bunny_720p_1mb.mp4")'
You could use autostart.sh in the config directory to run this command after kodi has started.
thanks for the idea, but it doesn't work sadly. I can start the cideo via ssh this way, but adding the line to autostart has no effect. isn't autostart.sh too "early"?
in the meantime I read Kodi Animation thread and XBMC Intro Movie.
it seems I need to make a copy of the integrated Estuary skin and edit home.xml or startup.xml. I hope I will find the time sometime next week.
following the suggestion in KODI 17 - Enable Playlist At Startup, I now use the "Partymode autostart" add on from the official repo. This is not perfect, as it displays the main menu for a couple of frames before it starts the video you select in its configuration. but for the moment it's good enough for me, so for anyone interested, this is certainly the easiest way to start LE with the right brightness on a S905x box and no HDR TV.
[hr]
thanks kszaq for answers and new build, will also test next week.