This is a source of fantastic frustration for me. Some modern Stoics are materialists, yet materialism is a point-blank rejection of the Unity of the Universe, which is a central plank of Stoic doctrine. Modern Stoicism seems to be fad for anti-religious folk who nevertheless want some meaning in their life. It makes no sense whatsoever in the hands of 'Stoics' like Massimo Pigliucci and becomes a muddle of poor thinking. Not at all what its founders intended.
The doctrine is being betrayed by people who don't understand it but want to bend it to their purpose. To understand it I would suggest studying Buddhist ethics and ontology and then comparing it to that of Stoicism. It can be seen that the latter is just a less well-explained and less well-informed version of the former. Both declare the Unity of the Universe, and both declare, 'only those who know they are not free know they are free'. This can hardly be a coincidence and it shows that Stoicism was well thought-out by its founders.
I have great sympathy for Stoics trying to make sense of the bowdlerised modern form often promoted. It's a lost cause. It does not make sense.