I think the photon being a boson (integer spin) is its own antiparticle.
I think if the universe was antimatter everything would be just the same.
Per wikipedia:
Antimatter may exist in relatively large amounts in far-away galaxies due to cosmic inflation in the primordial time of the universe. Antimatter galaxies, if they exist, are expected to have the same chemistry and absorption and emission spectra as normal-matter galaxies, and their astronomical objects would be observationally identical, making them difficult to distinguish.
I seem to remember that one decay pathway for some antiparticle is slightly different but thats about it.
This is not a generality, The W-boson is charged and we have thus W+ and W- particles around. None of them, are however classified as 'matter' as they are more connected to the interaction side.
In the case of the photon, it is however true that it is its own antiparticle.
Ah, thanks for the clarification!
Thank you, for the great question!