im stucked at a wierd problem, i had the same in retropi. im using a tablet for LAKKA, when i boot it, it is in portrait mode, and it still is in the menu, i cant find a way to change that, but i found that i can change to rotation of the Core/viewport, now here is the fun part, to rotation word but it rotate the portrait mode ( see pic)
Is there any way to fix this, i tried the screen_orientation in retroarch.cfg and tryed changing to resolution in video settings