FWIW this affects me too. I installed pretty much exactly the same installation (Ubuntu + Kodi + Steam) on two Mac minis, two days ago.
You can compare the devices if you wish - MacMini 4,1 and 5,1 respectively. 4,1 works fine, 5,1 does not. https://en.wikipedia.org/wiki/Mac_Mini#Specifications_3
Notable differences: Intel HD 3000 video on the broken 5,1 device, NVidia GT320M on working 4,1 device. Some other things as well.
Also, it seemed to coincide a few times with 'video card state changes', ie. screen saving on, etc. Could be total coincidence
FWIW this affects me too. I installed pretty much exactly the same installation (Ubuntu + Kodi + Steam) on two Mac minis, two days ago.
You can compare the devices if you wish - MacMini 4,1 and 5,1 respectively. 4,1 works fine, 5,1 does not. https:/ /en.wikipedia. org/wiki/ Mac_Mini# Specifications_ 3
Notable differences: Intel HD 3000 video on the broken 5,1 device, NVidia GT320M on working 4,1 device. Some other things as well.
Also, it seemed to coincide a few times with 'video card state changes', ie. screen saving on, etc. Could be total coincidence