The research I'm aware of has shown that light backgrounds help people with astigmatism because they cause constriction of the pupils to adapt to the increased

The research I'm aware of has shown that light backgrounds help people with astigmatism because they cause constriction of the pupils to adapt to the increased light coming in given low ambient light, which brings things into sharper focus for those with astigmatism. Of course not constricting the pupils is a major reason people like dark mode, and mobile devices have greatly increased the use of screens in environments with low ambient light. I suspect the only good solution is to support both light and dark modes universally.