Hi, I had the same problem with my S21, which I bought yesterday. Out of the box very grainy pictures. Then I noticed a software update was available, claiming to improve the camera (among other things). Now selfies look much better, I think they are still not as good as selfies from some competitors (I did a quick comparison), but they are definitely usable. Hope this could help. Bye.
Help! I bought s21 and selfie camera is sososoooo BAD why im so white ??? Even if i turn lightness down to -4 in beauty mode its still so white!!!! I took the HDR also off...still so whitewashed everything