Hey Namake,
I have a variant in the ABCC8 gene also. I've been managing / experimenting with low carb / keto and sometimes carnivore diet but have reintroduced a few carbs at times with mixed results. Currently I take Novorapid Insulin in the morning to deal with high morning numbers and sometimes with meals. My daughter has the same genetic variant, but has congenital hyperinsulinism which is a bit like the opposite of diabetes.
I've read as many studies as I can find on ABCC8 related diabetes and it seems that no two people with defects to this particular gene have the same experience.