Angular 8 - Lazy loading modules : Error TS1323: Dynamic import is only supported when '--module' flag is 'commonjs' or 'esNext'

You are using dynamic import so you have to change your tsconfig.json like this to target your code to esnext module

{
  "compileOnSave": false,
  "compilerOptions": {
    "baseUrl": "./",
    "outDir": "./dist/out-tsc",
    "sourceMap": true,
    "declaration": false,
    "module": "esnext", // add this line
    "moduleResolution": "node",
    "emitDecoratorMetadata": true,
    "experimentalDecorators": true,
    "importHelpers": true,
    "target": "es2015",
    "typeRoots": [
      "node_modules/@types"
    ],
    "lib": [
      "es2018",
      "dom"
    ]
  }
}

Also make sure to check tsconfig.app.json dont have module and target config something like this

{
  "extends": "./tsconfig.json",
  "compilerOptions": {
    "outDir": "./out-tsc/app",
    "types": []
  },
  "include": [
    "src/**/*.ts"
  ],
  "exclude": [
    "src/test.ts",
    "src/**/*.spec.ts"
  ]
}

Just adding to @Tony's anwser, you might also need to do the same (change to "module": "esnext" ) in the tsconfig.app.json. In my case the tsconfig.json was already using esnext as the module but the tsconfig.app.json was still using es2015 and that caused this error.

Just want to add my experience to @Tony's answer. After changing tsconfig.json it still showed an error (red underline). Only after reopening the editor (I used VSCode) did I see the red underline disappear.