在angular.json文件中更新"assets"的路径，例如：

"assets": [
    "src/favicon.ico",
    "src/assets",
    "src/mysite.html"
],

然后在组件中使用以下代码调用HTML文件：

import { HttpClient } from '@angular/common/http';
import { DomSanitizer } from '@angular/platform-browser';

export class AppComponent {

  myHtml: any;

  constructor(private http: HttpClient, private sanitizer: DomSanitizer) { }

  ngOnInit(): void {
    this.http.get('assets/mysite.html', { responseType: 'text' }).subscribe(data => {
      this.myHtml = this.sanitizer.bypassSecurityTrustHtml(data);
    });
  }
}

最后在模板中使用myHtml变量来显示HTML内容：