I'm on the same boat :/ My projects no longer build on Xcode 12, they work fine on XCode 11.7, which I luckily still have around I've been trying everything, but without a shred of indication of what's going on I'm absolutely lost Reverting to the legacy build system does not help Sometimes Xcode doesn't crash but still doesn't build, spitting out "unexpected service error: The Xcode build system has crashed. Please close and reopen your workspace." instead.

Of course right after I asked the question I notice this in the release notes 🤦‍♂️ Conditional views in columns of NavigationSplitView fail to update on some state changes. (91311311) Workaround: Wrap the contents of the column in a ZStack.