Error: NG0908: In this configuration Angular requires Zone.js

[alcfeoh]

When I open https://stackblitz.com/github/alcfeoh/ng-training-demos, I get the following error in the console:

Not sure what's going on, as this project works great outside of Stackblitz and does use Zone.js

[JeanMeche]

This is not a webcontainer based stackblitz, the angular.json is unused. You specifically need to import statically zone.js.
See for example https://stackblitz.com/edit/angular-next, where I have import 'zone.js'.