Xcode 12.2 SwiftUI previews issues

I notice some issues in Xcode 12.2 SwiftUI previews:

1. previews take a long time (several minutes) to show a simple preview: a button on IPod Touch device
2. debug mode on previews don’t work in most of cases: sometimes hangs on « loading » (with the loading icone turning), sometimes with a final message telling it took to much time to attach.
3. When rarely debug mode shows a green icone, button doesn’t seem to work as clicking on the button does not make it change the color of the text inside it and no message appears in the debug console if I put a print command in the action statement.

Xcode 12.2 final release (installed from Appstore)

Macos Big Sur 11.0.1 final release (installed from scratch for a clean installation)

Macbook Pro mi-2014