I absolutely cannot get my project to generate a SwiftUI preview, even for the simple "hello world" default. It builds successfully, spins for thirty seconds, then throws an error: TimeoutError: Timed out waiting for a thunk to build after 30.0 seconds. I've tried the usual stuff: Cleaning the build folder, erasing the derived data folder, rebooting, only running Xcode (in case it's a memory issue). No change. I don't see anything obvious in the diagnostic, but happy to post if someone wants to see it. It only seems to happen with this project. A different one (a SwiftUI app I wrote months ago) continues to work fine. This project is older, however, and has no existing SwiftUI code. It happens in both Xcode 11.5 and 12.0b2. My machine is a 2016 13" MacBook Pro (four-port Touch Bar) with 16GB RAM and a dual-core i5. Any ideas on what else to try? This a major impedance for my iOS 14 updates...