Minimun required specs for Angular Prerender

angular.json

{
  "newProjectRoot": "projects",
  "projects": {
    "cr": {
      // ...
      "prefix": "cr",
      "architect": {
        "build": {
          "builder": "@angular-devkit/build-angular:browser",
          "options": {
            // ... the usual options for browser
          },
          "configurations": {
            "production": {
              "outputPath": "./host/client/",
              "index": "src/index.html",
	            // ... other
            }
          }
        },
        "server": {
          "builder": "@angular-devkit/build-angular:server",
          "options": {
            "outputPath": "./host/server/",
            "main": "server.ts",
            "tsConfig": "tsconfig.server.json",
	           // ...
            }
          },
          "configurations": {
            "production": {
              "fileReplacements": [
                {
                  "replace": "src/environments/environment.ts",
                  "with": "src/environments/environment.prod.ts"
                }
              ],
              "optimization": false,
		          // ...
            }
        },
        "prerender": {
          "builder": "@nguniversal/builders:prerender",
          "options": {
            "browserTarget": "cr:build:production",
            "serverTarget": "cr:server:production",
            "guessRoutes": false, // guessing outputs all routes
            "routes": [
              "/projects/create",
              "/projects/1",
              "/example",
              "/" // this will generate index.original.html in the client folder
            ]
          }
        }
      }
    }
  }
}