Intel DRM no ouput - ideas needed

I have been using SDL2 without X11 for a couple of years now without problems (started on Raspberry Pi and lately on Intel Celeron J1800/J1900 boards).

Last week we got new boards with a Pentium J2900 which according to specifications should have the same generation CPU/GPU as the Celeron J1900 but with this board there is no video output from my SDL application.

Application detects KMSDRM driver, and looking at “intel-gpu-top” output the Render/3D part of GPU is working - gets busy when running my application - but Video/Blitting parts stay on 0%.

I went it further to make a simple test with using the simple demo code from the SDL Wiki.

Little more information about the GPU, it has HDMI and VGA output, I connected both outputs to monitors and it does show output of the Linux console (in modeset - so graphics mode is working) and after I start the test application the VGA output turns off - no signal detected.

Any suggestion on how to tackle this problem would be greatly appreciated as it does currently hinder me to continue my project, for which the current solution I have is to use X11 as base, but would really like to stay in my current configuration.

Thanks to any suggestions!