Xcode 12.3 is not responding a few seconds after opening it
Solution 1:
This is a recently reported bug with Xcode 12.3. I am not aware of any response from Apple yet, but you might be able to fix this issue by turning off the over-the-air test device builds.
- Top Menu: Window > Devices & Simulators
- Uncheck "Connect via Network" for each physical device
I recommend filing bugs with Apple and watching the forum thread about this.
You also revert to Xcode 12.2.