I am using the syntax for import bootstrap 4 library for static file
<link rel="stylesheet" type="text/css" href="../node_modules/bootstrap/dist/css/bootstrap.min.css">
angular.json
{
...
"architect": {
        "build": {
          "builder": "@angular-devkit/build-angular:browser",
          "options": {
            "outputPath": "dist/angularapp",
            "index": "src/index.html",
            "main": "src/main.ts",
            "polyfills": "src/polyfills.ts",
            "tsConfig": "tsconfig.app.json",
            "aot": false,
            "assets": [
              "src/favicon.ico",
              "src/assets",
              "src/browser-not-supported.html"
            ],
            "styles": [
              "src/styles.less"
            ]
            ...
          }
}
...
browser-not-supported.html
<link rel="stylesheet" type="text/css" href="../node_modules/bootstrap/dist/css/bootstrap.min.css">
Results:
Dose anyone have same problem?
Thanks!

 
     
     
     
    