Christian theology has its own version of this problem: if God is the source of everything and sovereign over all, how is evil not ultimately from God? Isn’t a difficulty being pressed on monism that theism hasn’t resolved either?

The parallel should be conceded and the difference stated. Theism distinguishes Creator from creation and locates evil in creaturely will, so evil is not part of God, though the question of why God permits it remains and is treated in the Problem of Evil case. Monism has no such distinction available, so evil must be either divine or illusory. Both views have a problem of evil; they are different problems. The Christian view thinks the monist’s is harder, since it has to deny that evil is finally real, but it says so while acknowledging its own.