Thanks for your solution.
You simply followed the guide on top of the existing (not working) Chromium?
Possibly the install of xorg
refreshed some xorg configuration that made things working. On Odroid XU4 e.g. some video driver update required changes in xorg.conf, although in that case it was required for Kodi.
Running Chromium desktop icon or our script (from console, outside of desktop) does still not work?
The Chromium options provided by the guide (and our script) cannot be the reason since desktop icon without any options fails/failed as well. Also the options (should) have nothing to do with the X server.
The method is mostly comparable with starting Chromium from desktop. Openbox is a X server session as well, lightdm the classic desktop login UI which we also use for desktop login (if chosen).