How to Solve the "An unhandled exception occurred: Schematic "page" not found in collection "@ngxs/schematics"" in ionic 4

When you switch to @ngrx/schematics as default collection which by default extends @schematics/angular, you can only uses schematics relevant to angular and ngrx. You have to switch to @ionic/angular-toolkit collection as default in order to use ionic schematics.

To use @ionic/angular-toolkit as default collection use ng config cli.defaultCollection @ionic/angular-toolkit.

You'll have to switch between @ngrx/schematics and @ionic/angular-toolkit because the CLI doesn't support multiple default collections. there is PR which track that issue. Check it out.