But, there is proof. DM acts as a gravity lens. All observers can see it from Earth, though in-directly, like gamma ray detection. Something big encases the all the galaxies. It is how we discovered it. Galaxies rotate as if they were a solid object and not a fluid of stars swirling in their own gravity. Their edges are velocity locked to the center. Impossible? NO. Observable
Just like we know x-rays are not visible but they are there., We can use X-rays. These gravity clouds (Dark Matter) are "there." We can "see" them in the same way we "see" x-rays. These gravity clouds bend light. And photos can be taken of the magnified light. Those can be mapped back to the shape of the gravity cloud.
But, is it matter, or just thin areas in the fabric of the quantum dimensions? Gravity is so weak, a billion times weaker than EM. If you have regions of stronger gravity, it could help the idea in Quantum World Theory, that most of our gravity, quite luckily is elsewhere, and not here, to crush us into a Big Bang again.
The displaced gravity could be along one the 8 other quantum dimensions. But, around a lot other Matter, say, a galaxy of it, more gravity leaks into our 4D space, quite significantly.