OK GPU is working actually, had to input this command to get it to work. Part of it is in the readme.php in the repository where the images have been uploaded by the guys @ LoveRPi.com
sudo update-alternatives --install /usr/local/lib/aarch64-linux-gnu/mali mali /opt/libre-computer/model/aml-s805x-ac/mali/lib/aarch64-linux-gnu/gl4es 100
then using sudo update-alternatives --config mali chose the gl4es entry just added
after that glxinfo and glxgears worked! FPS counter and everything.
Debian images README: http://share.loverpi.com/board/libre-computer-project/libre-computer-board/image/debian/README.php
Total Linux noob by the way but I like to tinker. README.php has no indication of this gl4es entry, although it is included in the image.