I have to revise my statement above.
I was able to solve the problem by uninstalling Playgrounds completely and then reinstalling it.
Unfortunately, I can't explain what the problem was with the first uninstall.
The only difference in my second attempt was that I both backed up and then deleted all my Playgrounds and uninstalled it in an administrative (a different) account.
Topic:
UI Frameworks
SubTopic:
SwiftUI
Tags: