The usual argument against the existence of antimatter galaxies is that we would be seeing somewhere, a matter galaxy colliding with an antimatter one. However, that assumption is based on the Cold Dark Matter model, which asserts that gravity was able to defy the uniform expansion of space, and pool together into galaxies. However, if galaxies were formed from the expansion of space, then there was a never point in the universe’s history in which gravity was able to defy expansion. Rather, gravity and expansion worked together to form the current structure.
If the expansion of space was caused by early matter/antimatter annihilations, as I assert, then whenever the two antiparticles collided, they expanded the space between them. This segregates matter clusters from antimatter clusters, perpetually moving further away from each other. So we should never see a matter galaxy collide with antimatter one.
The Standard Model’s solution to asymmetry is a shrug. The math says that matter and antimatter should have been created in exact equal amounts, but the Standard Model just handwaves at it now.