If you want more reading material, these are links to articles regarding mask effectiveness that the head of my local county health department provided today when challenged by one of the judges about mask recommendations. The delta variant, which is on the increase locally, had prompted the interaction between the health department and the judge. I don’t know if any of the articles touch specifically on the issue of equal effectiveness for all COVID variants. I would wonder if newer variants have existed long enough for anyone to do studies of variant-specific mask effectiveness.
An evidence review of face masks against COVID-19 | PNAS
How effective is a mask in preventing COVID‐19 infection? (nih.gov)
Making sense of the research on COVID-19 and masks (byu.edu)
Face masks effectively limit the probability of SARS-CoV-2 transmission | Science (sciencemag.org)