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.

I have encountered a very similar problem on my end. Since updating to Playgrounds version 4.2.1 (from 4.0) neither the old Playgrounds "Learn to code 1", "Learn to code 2" nor a current one like "Get Started with Apps" work. I am also able to run Swift based apps in Xcode. I have tried reinstalling Playgrounds, reinstalling Xcode. All without success. I also contacted Apple support (chat), but they couldn't help me. They suggested me to reinstall Playgrounds. Mac OS 13.1 Xcode: 14.2 Playgrounds: 4.2.1 This is what the error message looks like when I run an "old" Playground (e. g. "Learn to Code 1").