What consequences does a positive muon anomalous magnetic moment have for astronomy?
This is unlikely to have any implications for astronomy. They may have seen an extremely small deviation from the predictions of the standard model. The result may actually have to do with technical issues in theoretical methods, not with any new physics: https://arxiv.org/abs/2002.12347 . Even if it does have implications for new physics, there is no reason to believe that it would have implications for astronomy. It could, for example, be an indication of the existence of a new unstable particle with a high mass, whereas dark matter needs to be made of stable particles.