Big Sur on a 21.5-inch iMac from 2010

https://preview.redd.it/1e47e9qcakeg1.png?width=1920&format=png&auto=webp&s=77209e502605967f30a9395a76d25f285fb69d5b

So far, it works pretty well, and the fans are a bit quieter than on High Sierra! There are some minimal lags. However, this iMac has 6 GB of RAM, so +2 GB compared to the base model, so bear that in mind if your 2010 iMac has only 4 GB of RAM!