‘Sort of’, I did spend a lot of time working on DMG/Pocket compatibility at the start as these are the systems I’m the fondest of.
Earlier versions ran better on DMG, although quite a lot of effects had to be stripped out for performance or other reasons (reflections, weather etc), some palette lighting effects and a reduction in actors and AI.
Since v4 of GB Studio there’s been a further hit to the performance on DMG, so I’m currently completing development as Color devices and upwards, with plans to go back and optimise, cut if necessary and decide if the experience can be made good enough to include DMG support, hopefully so but afraid it’s not a definite.