Hi Substring,
Thanks a lot for your support and for your great work on GA !
As you nailed it, the issue was solved by booting GA in legacy mode (not trivial though because I had to go in bios setup and change boot order to do that).
Then the VGA display was detected and the install went fine.
One minor issue I had after the install is that I had to edit /boot/syslinux/syslinux.cfg in order to lower resolution to 640x480 which was initially set to 800x600 and caused the jammaASD to filter the output signal.
Other than that everything works fine, excepting an issue with button mapping that activates the underlying windows management keyboard shortcuts:
For example, pressing button 1&2 and right direction display the virtual desktop switch widget.
I removed all keyboard shortcuts present in ~/.config/openbox/lxde-rc.xml file. It works great if I launch attract mode from LXDE, no more window manager interaction.
But If I choose Attract Mode as main window manager, the problem persists.
I guess that there is a file that manage key bindings globally but don't had time to find it yesterday.
I will go on my investigations today but if you know which file I have to edit (or operations steps), please let me know.
Otherwise, thanks for your effort bringing GA better and up to date, that's really much appreciated.
Keep up the good work.