This review from 2017 highlights many of the studies that have focused on isoflavones, which are a subgroup of the flavonoids, they include but are not limited to genistein, daidzein and biochanin A. These isoflavones have varying estrogenic activity and isoflavones have been proposed as natural SERMs.
Rietjens IMCM, Louisse J, Beekmann K. The potential health effects of dietary phytoestrogens. Br J Pharmacol. 2017;174(11):1263-1280. doi:10.1111/bph.13622 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5429336/