Antimatter may have negative gravity properties, which therefore would fill the intergalactic voids (trying to be as far away from any other particle as possible) which may result in an illusion of dark energy. Antimatter repels everything, even antimatter. This causes continuous "expansion" as antimatter increases the space between itself and creates larger and larger volumes of empty space by repulsion. This may be detectable if we can find gravitational repulsion effects of antimatter particles. This can solve the dark matter problem and matter/ antimatter asymmetry also if true. this repulsive force everywhere in space can potentially help bind matter more tightly in galaxy pockets which can act as a sense/illusion of increased gravity for the galaxies by "pushing" them tighter, which may also solve dark matter.
Antiparticles are distributed throughout the void and repel every type of matter surrounding it.
The universe may not be accelerating, the light from far away galaxies may collide with the antimatter particles in the void every so often, which absorb their energy, giving an illusion of red shifting. The farther away galaxies are the more collisions and therefore more "red shifting".