Same problem on Xcode 12.2, it was working fine for a few minutes, and then it just stops. It won't print anything on the console, but it does still tell me where I make mistakes. I left it running for like an hour now and still nothing. I restarted Xcode multiple times and it doesn't fix anything for me! Apple if you are reading this, this is a major problem that you have to fix as soon as possible! I use playgrounds all the time to test my codes and ever sense I got Xcode 12 it just won't work properly. im on a MacBook Air (Retina, 13-inch, 2019) with Big Sur version 11.0.1