While we can assume that our galaxy is made out of matter the same cannot be said about galaxies further away. If matter and antimatter split into clusters it’

While we can assume that our galaxy is made out of matter the same cannot be said about galaxies further away. If matter and antimatter split into clusters it’s possible that some galactic clusters formed out of anti matter and some out of matter. This for a time was the prevailing theory however for the most part we assume now that the universe is indeed made out of matter because we do not see annihilation events throughout the observable timeline of the observable universe. Also if matter and antimatter are still at 1:1 ratios one would expect to detect annihilation events across the galactic void since space between galaxies isn’t completely empty and the current temperatures are too cold for annihilation to occur at any rate that would indicate that symmetry wasn’t broken during the early universe.