In the case of people of African descent, I think we _do_ have a specific candidate for a biological difference affecting COVID-19 outcomes. A randomized clinical trial found that
+"Autumn COVID-19 surge dates in Europe correlated to latitudes, not to temperature-humidity, pointing to vitamin D as contributing factor"
+https://www.nature.com/articles/s41598-021-81419-w
+
https://www.sciencedirect.com/science/article/pii/S0960076020302764
https://pubmed.ncbi.nlm.nih.gov/16549493/