[hymenopter4]

That does not invalidate the concept. Gravity has not been found to be an incidental phenomenon measurable for anything other than matter's accumulation.

In the observable universe (regardless of theories and expressions penned on paper) gravitational forces are always induced by massive material objects, including the remnant artifacts of deceased stars. To suggest otherwise is to walrus the conversation.

[millstone]

Dark matter measurably gravitates and is not a “massive material object.”

[hymenopter4]

Dark matter has yet to be defined as anything other than an observed effect on the behavior of matter. Something (and indeed a thing, if anything, ergo matter) we think is probably there.

Being a theoretical hypothesis, formed to explain observations, it remains a side-effect of accounting and inference, and has not been located directly.

Show me why you believe it is a thing. Show me where you have found it. Tell me why it isn't actually matter.