I'm pretty sure no one knows how GR and QM come together.
Quantized inertia?

It's easy to imagine that an object is surrounded by an enormous information horizon. For an object that is not accelerating, it's a sphere... beyond the sphere, light can never reach the object. But what happens at the horizon? At the event horizon of a black hole, we have Hawking radiation... virtual particle pairs that become separated Well, the same is true for this information horizon... from the pov of the object, virtual particles become separated, giving rise to real particles... a type of Hawking radiation.

Now, an object that is not accelerating is surrounded by a sphere, but what if the object accelerates? In the direction of acceleration, the horizon will expand, while behind the object, it will contract. This creates an imbalance which can be thought of as similar to a Casimir effect, only on a universal scale... certain wavelengths of particles will be accessible to the object in front, but not from behind. This creates a radiation pressure that is greater in the direction of acceleration. Inertia is born! This pressure manifests itself as a resistance to acceleration, the very definition of inertia.

For reasons I don't understand, this theory implies a minimum acceleration, which in turn might explain the motion of galaxies without the need for dark matter. Essentially, the outer edges of the galaxy has lost inertial mass, and so can move faster than Newtonian dynamics would expect them to.

There are problems with this theory, the biggest one is that it completely violates the equivalence principle. At very low acceleration (below the minimum threshold mentioned), gravitational mass and inertial mass are not the same. But some people seem to think that this theory is a promising one, in that it might unify GM and QM. I'm not so sure about that, but it's definitely interesting.

Here's a 20 minute clip if you an be bothered...