You shouldn't need

@import "~bootstrap/dist/css/bootstrap.css";

or

<link rel="stylesheet" href="../node_modules/bootstrap/dist/css/bootstrap.css">

Putting bootstrap.css into angular.json > styles should be enough.

You should also initialize jQuery in app.component.ts

Because Bootstrap (still) uses jQuery, you should consider using something like primefaces.org/primeng It's based on Bootstrap (loosely) and doesn't require jQuery. Ie: using Bootstrap with Angular isn't ideal now a days.